Ferroelectric liquid crystals for nonlinear optics applications

ABSTRACT

The present invention provides ferroelectric liquid crystal and liquid crystal compounds, among which are compounds which possess large X.sup.(2), i.e. second order nonlinear susceptibility and thus make them useful in optical and nonlinear optical applications. The invention includes chiral nonracemic compounds of formula ##STR1## where one of n or m is 1; k is 1 and B is COO or OOC; R&#39; is a straight-chain or branched alkyl or monoalkene group having from 1 to 20 carbon atoms where one or more of the non-neighboring carbon atoms in R&#39;, except any unsaturated carbon atoms, can be replaced with O, S or a Si(CH 3 ) 2  group; and R&#39; is a chiral nonracemic tail group selected from the group consisting of --O--C*H(CH 3 )R c , --O--C*H(CH 3 )COOR d  and --O--CH 2  C*HF--C*HF--R 6  in which the * indicates an asymmetric carbon enriched in one stereoconfiguration which for --O--CH 2  C*HF--C*HF--R e  is either the (S,S) or (R,R) stereoconfiguration wherein: R c  is a straight-chain or branched alkyl or monoalkene group having 2 to 15 carbon atoms; R d  is a straight-chain or branched alkyl or monoalkene group having 2 to 13 carbon atoms and R e  is a straight-chain or branched alkyl or monoalkene group having 2 to 11 carbon atoms wherein in R c , R d  or R e  one or more non-neighboring carbon atoms, except any unsaturated carbon atoms, can be substituted with an O, S, or Si(CH 2 ) 2  group.

This invention was made with at least partial support of the UnitedStates Government which has certain rights in this invention.

This application is a continuation of U.S. application Ser. No.07/690,633, filed Apr. 11, 1991, now abandoned.

FIELD OF THE INVENTION

The present invention relates to liquid crystal compounds possessingmolecular and supermolecular structure providing large bulk electronicsecond order nonlinear optical hyperpolarizability X.sup.(2) in easilyprocessible optical quality films. These materials, which areferroelectric liquid crystals (FLCs), have application in fast opticalprocessing and switching devices.

BACKGROUND OF THE INVENTION

The bulk electrical polarization P of a material in an electric field(or the electric part of an optical field) may be expanded in powers ofthe field according to equal, where P_(S) is the spontaneouspolarization (i.e. polarization present in the absence of applied field,X.sup.(1) is the linear polarizability, X.sup.(2) is the second ordernonlinear hyperpolarizability, or second order nonlinear susceptibility,X.sup.(3) is the third order nonlinear hyperpolarizability or thirdorder nonlinear susceptibility. The subscripts i, j, k etc. correspondto the Cartesian coordinates x, y, or z for the system (Williams, D. J.,(1984) Angew. Chem. Int. Ed. Engl. 23:690-703). ##EQU1##

The sum of all terms to the right of P_(S) in equal give the inducedbulk polarization in response to an applied field or fields. Thespontaneous polarization P_(S) is a vector, while the susceptibilitiesX.sup.(1) etc. are tensors with component values which are dependentupon the frequency of the applied fields. The square of X.sup.(1) drivenby a DC or low frequency AC field is proportional to the dielectricconstant of the material, while the square of X.sup.(1) driven by anoptical frequency AC field is proportional to the refractive index ofthe material. All materials possess non-zero X.sup.(1) and X.sup.(3).There are certain symmetry requirements for P_(s) and for .sup.(2)),however. Thus, in order to possess non-zero P_(s), the system must havepolar symmetry. Furthermore, within the electronic dipolar model,X.sup.(2) is zero unless the system possesses noncentrosymmetricsymmetry (acentric). All materials with polar symmetry are acentric, butnot all acentric materials are polar. Thus it is possible for a materialto possess strictly zero P_(s) by symmetry, but non-zero X.sup.(2) inthe electronic dipolar model.

Materials possessing non-zero X.sup.(2) exhibit many effects of greatcurrent and potential utility. These include but are not limited to: 1)Second harmonic generation (SHG); 2) Sum and difference frequencygeneration; 3) Optical parametric amplification; 4) Opticalrectification; and 5) A linear electrooptic effect (Pockel's effect).Effects 1, 2 and 3 depend upon the induction of optical frequency ACpolarizations (or charge flow in the material changing in sign ormagnitude at optical frequencies) in the material in response to opticalfrequency AC applied fields, and therefore derive from optical frequencyX.sup.(2) values. These values of X.sup.(2) may be termed "ultrafast".

In general, the ultrafast X.sup.(2) is a lower limit, and the inducedpolarization in response to lower frequency applied fields will ingeneral be larger (i.e. X.sup.(2) generally increases with decreasingdriving field frequency, though the increase is not monotonic). Verylarge increases in X.sup.(2) occur at frequencies where resonantabsorption of the driving radiation occurs. For the applications ofinterest in this invention, however, non-resonant interactions of thematerial with driving and induced fields are preferred.

Currently X.sup.(2) materials are utilized extensively for frequencyconversion (effects 1 and 2 above), and more experimentally inelectro-optic modulators (effect 5). Typically these materials areinorganic single crystals (for example single crystals of potassiumdihydrogen phosphate (KDP) or lithium niobate (LiNbO₃). For manyapplications, particularly in the emerging opto-electronics andphotonics industry, easily processible thin films possessing X.sup.(2)are of great potential utility. Uses of X.sup.(2) thin films include,for example, electro-optic switching and frequency processing inguided-wave geometries. Guided-wave geometries are useful in, forexample, integrated optical circuits or specialized devices such asoptical parametric amplifiers or electro-optic modulators.

For some of these potential applications, the film must work in concertwith other materials, such as silicon or other semiconductor integratedcircuits. This requires that the film be processed onto or with thesemiconductor or other material in a controlled way, affording a hybriddevice. In some thin film applications inorganic crystals are relativelydifficult to utilize, being difficult to hybridize with semiconductors.

It has been known for some time that organic materials possess potentialadvantages in X.sup.(2) applications (see Prasad, P. N., (1990) Chem.Mater. 2(6):660-669). These include: 1) Easy processibility relative toinorganic crystals; and 2) Potentially large and relatively easily tunedvalues of the X.sup.(2) components. The potential for easyprocessibility derives by analogy to the relatively easy creation of,for example, organic polymer and liquid crystal films of opticalquality. The potential for large X.sup.(2) derives in part fromexperimentally determined values of the molecular susceptibilities oforganic molecules. Thus, the polarization of a molecule in the presenceof applied electric fields is given by equ 2, where μ is the moleculardipole moment, α is the molecular linear polarizability, β is themolecular second order hyperpolarizability, etc. ##EQU2##

Using the technique of, for example, electric field induced secondharmonic generation (EFISH) in isotropic solutions, it is possible tomeasure the magnitude of certain components of β for many organicmolecules. A fairly good estimate of X.sup.(2) may be made based uponthese β values, and using such estimates, it may be shown that X.sup.(2)for organic materials may in principle be much larger than thoseexhibited by inorganic crystals (Prasad, P. N., (1990) supra).

Finally, the potential for tunability derives from the great structuraldiversity of organic molecules combined with some relatively simplemodels for the molecular origins of β. Thus, while the level ofunderstanding of the molecular origins of β is not quantitative, it iseasy to predict-qualitatively the magnitude of β expected for neworganic molecules using the "two-state model" (Williams, D. J., (1984)supra and Prasad, P. N., (1990) supra). In this model, using the valencebond structures of the ground and first electronically excited statesone may calculate the expected β value in response to driving fields farfrom resonance. At the current state of the art, these calculations giveonly a qualitative picture of the hyperpolarizability of the molecules.

More simply, it is generally appreciated that the molecular β increaseswith increasing difference in molecular dipole moment of the groundstate and first electronically excited state of the molecule.Furthermore it is generally known that this occurs when a donor groupand an acceptor group are oriented ortho or para on a benzene ring.Donor and acceptor refer to the ability of the group to either donateelectron density (donor) or donate positive charge density (acceptor) toan aromatic ring. When the donor and acceptor are regiochemically placedon the benzene ring such that negative charge transfer from the donor tothe acceptor can occur according to simple resonance arguments (i.e.they are conjugated), then a large β should result. With a singlebenzene ring the conjugated substituents are ortho or para, as indicatedin the following diagram for p-nitroaniline--a prototypical organic NLOmolecule. An axis, termed here the "β axis", may be defined for suchmolecules. This axis is along the line connecting the donor substituentwith the acceptor substituent. If the molecular coordinate system isdefined such that the β axis is along y, then β_(y),yy will be a largecomponent of the β tensor. ##STR2## Furthermore, it is understood thatthe larger the distance between the donor and acceptor, the larger the βwhich will result for a given donor-acceptor pair (β goes upapproximately as the square of the distance separating the donor andacceptor). Thus, para nitroaniline has a larger β than the ortho isomer.Furthermore, conjugation between the donor and acceptor can be across alarger grouping than one benzene ring, as long as the conjugation is notbroken. Thus, stilbenes, tolanes, and diphenyl azo compounds substitutedat the p-p' positions with donor and acceptor groups possess very largeβ values, with the β axis on the line between the donor and acceptor,stilbenes and azo compounds larger than tolanes. The prototypicalorganic molecule with very large β is disperse red 1, a diphenyl azocompound, whose ground state structure and charge transfer resonancestructure are: ##STR3##

Furthermore, it is known that when β gets large with increasingconjugation, then the farthest red resonant electronic absorption peak(γ_(max)) is red-shifted, leading to increased resonant absorption atlonger wavelengths close to γ_(max) relative to a molecule with lessconjugation or a smaller conjugation length. For some applicationsblue-shifted resonant absorption (i.e. towards the UV, affording morevisible clarity) is advantageous, such as frequency doubling into theblue part of the visible spectrum. For some applications, such aselectro-optic modulators which typically operate at wavelengths whereglass fiber has the minimum dispersion (>1.0 μm) the red shift inγ_(max) for the NLO molecules may not be a disadvantage.

From the above discussion and data it can be seen that organic moleculesmay be designed qualitatively to possess a given β value consistent witha given γ_(max). It is not the subject of this invention to teach newdonor-acceptor pairs or new conjugating spacers. Rather, this inventioncan take advantage of most known or new donor-acceptor pairs, and alsoknown or new conjugating spacers.

It is known that in order to possess useful X.sup.(2) the NLO moleculesmust be combined to create a material, in some cases a thin film, and insome cases a bulk sample, typically much larger than the size of themolecules, but possessing acentric symmetry (Williams, D. J., (1984)supra and Prasad, P. N. (1990) supra). Furthermore, it is sufficient butnot necessary for the material to possess polar order. Furthermore, itis understood that when the donor, acceptor and conjugating spacer (theB axis) lie on or close to a polar axis of a medium with polar order,and are oriented along the polar axis in a polar fashion, then theX.sup.(2) of the material is optimized for that donor-conjugatingspacer-acceptor unit.

Several methods for achieving the combination of the NLO molecules intothe desired X.sup.(2) material are known. These include: 1) Singlecrystals or oriented microcrystalline solids (see for example Marder, S.R., et al., (1989) Science 245:626-628); 2) Langmuir-Blodgettmultilayers or self-assembling multilayers (see for examplePopovitz-Biro, R., et al., (1988) J. Am. Chem. Soc. 110(8):2672-2674)and Tillman, N., et al., (1988) J. Am. Chem. Soc. 110:6136-6144); and 3)Electrically poled polymer films (see for example Williams, D. J. (1984)supra, Dembek, A. A., et al., (1990) Chemistry of Materials 2(2):97-99,and Park, J., et al., (1990) Chem. Mater. 2:229-231). The presentinvention provides a new method for achieving the NLO material bycombining donor-conjugating spacer-acceptor arrays (the β axis) orientedwith good polar order along the polar axis of ferroelectric liquidcrystal samples, which are typically but not necessarily thin films.Furthermore, the method of the present invention possesses importantadvantages over any of the previously existing methods.

It is known that often the molecular β impart a large molecular dipolemoment in the ground state along the β axis, and that uponcrystallization, these units often orient antiparallel to affordcentrosymmetric symmetry in the crystal. Thus, for example,p-nitroaniline, while possessing a useful β value, gives centrosymmetriccrystals with very small or zero X.sup.(2) (exactly zero in theelectronic dipolar model).

It is also known that it is often possible by relatively smallmodifications to the structure of the molecules, to obtain polarcrystals with good polar orientation of the β axis along the polar axis.Thus, for example, when the p-nitroaniline molecule is substituted witha methyl group ortho to the nitro grouping, the resulting methylnitroaniline (MNA) fortuitously crystallizes with appropriate symmetryfor X.sup.(2), and indeed MNA crystals have a very large X.sup.(2) valuewith moderate resonant visible absorption.

It is also known that organic single crystals, especially those formedfrom non-ionic molecules, often called Van der Waals crystals, aretypically difficult to process into optical quality materials. This maybe due to the fact that crystal growth is a kinetic, rather than athermodynamic phenomenon, and crystal nucleation at multiple sites leadsto the formation of domain wall defects which scatter light. Thescattering of light from defects is highly undesirable in NLO materials.Furthermore, it is also difficult to control the organic crystal growthin thin film applications, especially for hybrid devices where theorganic film must be oriented correctly on a specific substrate surface.

This lack of processibility presents a major disadvantage of organiccrystals for X.sup.(2) applications. The problems with crystals led tothe invention of several alternative approaches, especially for thinfilm applications. Two such approaches involve growing a crystalline ornon-crystalline film from a substrate one molecular monolayer at a time.In the Langmuir-Blodgett method, NLO molecules are synthesized such thatthey also form monolayers (LB films) on water. This is achieved bycontrolling the hydrophilicity and hydrophoebicityof parts of themolecules, and can lead to excellent control over the orientation ofmolecular fragments, including the functional arrays affording large β,in the monolayers on water.

By careful dipping of a substrate into the monolayer film it is possibleto deposit the monolayer with good structural control onto the surfaceof the substrate. Additional dipping cycles, with additional methodsneeded to achieve bulk polar order, can afford multilayers withappropriate structure for X.sup.(2). In a somewhat related process, itis possible with correctly designed NLO molecules possessing reactivefunctional groupings to dip a substrate into an isotropic solution ofNLO molecules, and obtain a structurally well-defined monolayercovalently bound to the substrate. Chemical modification of theresulting new surface to introduce appropriate reactivity at thesurface, followed by another dipping cycle, etc., can afford multilayerswith structure appropriate for NLO applications.

In both of these approaches, many dipping cycles (>1,000) are requiredto achieve materials of good utility for NLO applications. Furthermore,the structural stability of the resulting multilayers, especially the LBmultilayers, is not currently known. In addition, the optical qualityachievable for such films is not known. Finally, these techniques areinefficient in time, and presumably cost, and limit the possiblegeometries of the β axis relative to the substrate surface since for allknown examples the polar axis must be normal to the substrate surface.These factors represent disadvantages of the multilayer approaches forcreation of X.sup.(2) thin films.

Molecules possessing a dipole moment and β axis (typically colinear) canbe either doped into a polymer matrix, or covalently attached to thepolymer matrix. When such polymer matrix is then heated to a temperatureabove a glass transition temperature and subjected to an electric field,the NLO molecules will tend to align with their dipoles parallel to thefield, affording the bulk polar order giving X.sup.(2). If the field isremoved, the NLO molecules rapidly revert to their random state,destroying the X.sup.(2) of the sample. However, if the sample is cooledwith the field applied below the polymer glass transition, then thepolar order induced by the field can be "frozen" into the sample. Thefield can then be removed to give an optical quality film with usefulX.sup.(2).

It is known that such films are typically unstable over time. That is,the NLO molecules, whether covalently attached to the polymer molecules,or doped into the polymer, will over time randomize their orientation,destroying some of the X.sup.(2) of the sample. While many approachesfor stabilizing the polar order present in such films are being explored(chiefly cross-linking of the polymer lattice to stabilize the positionsof the molecules temporally), the polar order in such films in theabsence of applied fields is inherently unstable thermodynamically. Inaddition, the degree of orientation of the molecular β axis along thepolar axis achievable with the largest possible poling electric fieldsis relatively poor. The good optical quality of non-crystalline ormicrocrystalline polymer films, and their relative ease of manufacture,are advantages of the poled polymer method for creating X.sup.(2) films.The thermodynamic instability of X.sup.(2) poled polymers and the poordegree of structural control in the films are disadvantages of themethod.

In liquid crystals (LCs), mesogen molecules spontaneously self-assembleinto true fluids which are anisotropic. Typically, the mesogens arerod-shapped molecules. The long axis of the molecules, and also theoptic axis of the LC phase, is called the director, which is representedby the unit vector n. It is relevant for the present invention that forall known LC phases, all properties of the phases are invariant withsign of the director (often represented as n→n). Thus, there is nospontaneous polar order along the director for any known LC phases.

When the liquid crystal is such that the molecules self-assemble into alayered structure, the liquid crystal phase is called smectic. SmecticLCs may be considered as a stack of 2-dimensional fluid phases eachapproximately one molecular length in thickness. There are many smecticLC structures. In some of these, the director is tilted coherently withrespect to the layer normal (z), affording a tilted, layered structure.In this case, the thickness of the molecular layers is typically smallerthan the molecular length. The plane containing n and z is termed thetilt plane.

While there is no fundamental reason why smectic C phases cannot possessspontaneous polar order, to our knowledge no smectic C phase possessingsuch order has ever been reported. Thus, all known smectic C phasespossess the following symmetry elements for the phase: 1) A C₂ axis ofsymmetry normal to the tilt plane (satisfying the empirical fact thatn→nn); and 2) A σ (mirror) plane congruent with the tilt plane. Thus,known smectic C phases possess a center of symmetry, i.e. they arecentrosymmetric, and therefore possess zero X.sup.(2) in the electronicdipolar model.

When a medium is composed of chirally asymmetric molecules, such mediummust be acentric, since the medium cannot possess any reflectionsymmetry. This is true for all media, including specifically isotropicliquids, all LC phases, and all crystalline or amorphous materials(Giordmaine, J. A., (1965) Phys. Rev. 138(6A):A1599-A1606, Rentzepis, P.M., et al., (1966) Phys. Rev. Lett. 16(18):792-794). The chirality doesnot, however, force polar order on the system.

For example, it has been demonstrated that chiral, isotropic liquidssuch as solutions of sugar molecules in water possess non-zero X.sup.(2)due to the acentricity of the medium (Rentzepis, P. M. (1966) supra). Insuch isotropic liquids there is no polar order, and thus no possibilityfor orientation of a molecular β axis along a polar axis. In general, itis known that orientation of a large β axis along a polar axis is avalid method for achieving large X.sup.(2). It is known that theX.sup.(2) occurring in acentric isotropic liquids is small.

Furthermore, chiral molecules possessing large β are often utilized forgrowth of crystals for X.sup.(2) applications. Such crystals must beacentric, and may or may not possess polar order. However, even whenpolar order exists, in order to achieve large X.sup.(2) it is generallyappreciated that the β axis should be oriented along the polar axis. Ifthe β axis is not oriented along the polar axis, small X.sup.(2) willresult.

When molecules in the smectic C or any other tilted smectic phase aremade chirally asymmetric, then by symmetry considerations the phase mustpossess polar order in addition to acentricity. That is, all chiralfluid media (and non-fluid media) are acentric, but for known fluids,only in the tilted, layered LC case does the chirality also impart polarorder upon the system (Walba, D. M. (1991) Ferroelectric LiquidCrystals: A Unique State of Matter. In: Mallouk T. E., ed. Advances inthe Synthesis and Reactivity of Solids, Vol 1. Greenwich, Conn.: JAIPress Ltd 173-235). In the case of the smectic C phase, such a chiralsmectic C phase is denoted as the smectic C, phase, which must possesspolar order, its symmetry elements being limited to one C₂ axis ofsymmetry, congruent with the polar axis of the phase, and orientednormal to the tilt plane. Such chiral, tilted, layered LCs are the onlyknown fluids possessing thermodynamically stable polar order.

Typically, the polar order occurring smectic C* phases causes thespontaneous formation of a macroscopic electric dipole moment for thephase. The direction of this macroscopic dipole moment switches uponapplication of an external electric field, though external fields arenot required for the macroscopic dipole to exist. Chiral smectic C,phases, and other chiral tilted, layered LC phases, are thus typicallyferroelectric, and are often termed ferroelectric liquid crystals (FLCs)(Walba, D. M. (1991) supra). It is understood that this term includesall chiral, tilted, layered LC phases.

The macroscopic dipole moment of the phase present in the absence ofapplied electric fields is termed the ferroelectric polarization, P,which is the same as P_(s) in equation 1. This polarization derives fromthe orientation of molecular dipoles (μ in equation 2) along the polaraxis of the phase. The polarization P has a sign, which by arbitraryconvention is positive when P (from negative to positive poles) pointsalong the unit vector z ×n, and negative when P is opposed to z×n.Enantiomeric (i.e. mirror image) FLC phases possess exactly equalmagnitude but opposite sign of P (Walba, D. M. (1991) supra).

The experimental fact that FLCs possess polar order means that FLCs mustpossess non-zero X.sup.(2) in the electronic dipolar model. In addition,may FLC mesogens, including, for example, DOBAMBC, the first FLC everreported, also possess functional arrays expected to have large β. ThusrDOBAMBC and many other FLCs possess polar order and are composed ofmolecules with large β.

However, the measured values of the ultrafast X.sup.(2) in previouslyknown FLCs are very small. Table 1 lists the values of X.sup.(2) forseveral exemplary known FLC materials as measured by the anglephase-matched SHG technique (see Taguchi, A., et al., (1989) Jpn. J.Appl. Phys. 28(6):L 997-L 999. and Liu, J. Y., et al., (1990) OpticsLetters 15(5):267-269). Here, X.sup.(2) is given as value for thed-tensor coefficients (d=X.sup.(2) for SHG). For DOBAMBC and thecommercial mixture ZLI 3654, only d_(eff) is given. This value derivesfrom a geometrical combination of various d coefficients, and the squareof d_(eff) is proportional to the intensity of second harmonic lightoutput from the sample at the top on an angle phase-matched peak.Experiments providing the values of all non-zero components of the dtensor for the commercial mixture SCE 9 in the homeotropic alignmentgeometry have been accomplished, said values given in the table (Liu(1990) supra). Note that there is some correlation between thepolarization of the sample and the observed d_(eff). This correlationcan be indicative, but is not rigorous.

                                      TABLE 1                                     __________________________________________________________________________    Values of the ferroelectric polarization, SHG efficiency, and X.sup.(2)       (d.sub.eff and                                                                d coefficients), for representative previously known FLCs. Values for         some                                                                          common inorganic NLO crystals are included for comparison.                                        SHG       d                                               Entry          P    arb  d.sub.eff                                                                          coefficients                                    number                                                                             compound  (nC/cm.sup.2)                                                                      units*                                                                             (pm/V)                                                                             (pm/V)                                          __________________________________________________________________________    1    DOBAMBC.sup.a                                                                           -3   1    0.0008                                               2    ZLI 3654.sup.b                                                                          -29  40   0.005                                                3    SCE 9.sup.c                                                                             +33.6                                                                              160  0.01 d.sub.2,3 = 0.073                                                             d.sub.2,2 = 0.027                                                             d.sub.2,1 = 0.0026                                                            d.sub.2,5 = 0.0009                              4    KDP.sup.d                d.sub.3,6 = 0.038                               5    5% MgO:LiNbO.sub.3.sup.d d.sub.3,1 = -4.7                                __________________________________________________________________________     *Intensity of the second harmonic light at the top of the type 1 eeo angl     phasematched peak.                                                            .sup.a Vtyurin, A. N., et al., (1981) Phys. Status Solidi B                   107(2):397-402.                                                               .sup.b Taguchi (1989) supra.                                                  .sup.c Liu (1990) supra.                                                      .sup.d Eckardt, R. C., et al., (1990) IEEE Journal of Quantum Electronics     26(5):922-933.                                                           

As can be seen from Table 1, the values of the largest d coefficients(one measure of X.sup.(2)) for the known FLCs which have been evaluatedfor X.sup.(2) are small relative to the known X.sup.(2) crystal KDP.This may be due to a combination of two factors: 1) The β axis in FLCsis generally oriented along n, and there is no polar order along n; and2) The degree of net polar order, as evidenced by the magnitude of themacroscopic polarization, is poor.

In this invention we provide a general approach for obtaining moleculeswhich, when introduced into an FLC phase either as a pure mesogen, orcomponent of an FLC mixture, will impart large X.sup.(2) to the FLCphase by orientation of a β axis of the molecules along the polar axisin the FLC phase, and by achieving a high degree of polar order.

Typical thermotropic LC mesogens or components possess structurescombining a rigid core with two relatively "floppy" tails (see Demus etat. (1974) Flussige Kristalle in Taballen, VEB Deutscher Verlag furGrundstoffindustrie, Liebzig for a compilation of the molecularstructures of LC molecules). FLC materials have been prepared byintroduction of at least one stereocenter in at least of of the tails.Thus, referring to the general formula A, the rigid core can be, forexample, benzylideneamino cinnamyl, biphenyl, phenylbenzoate,phenylpyrimidine or biphenylbenzoate, X and/or Y can be oxygen or CH₂,R' is an achiral alkyl grouping with from five to twelve carbon atoms,and R* is a chiral moiety. ##STR4##

The FLCs reported to date are generally designed for use in theClark-Lagerwaal surface stabilized FLC light valve (Clark, N. A., etal., (1980) Appl. Phys. Lett. 36(11):899-901), or other similar lightmodulation technology involving large nuclear motions of the FLCmolecules for switching in response to applied DC fields or lowfrequency AC fields (<100 MHz). For such FLCs, an important figure ofmerit is the characteristic response time of the cell (τ), givenapproximately by equ 3: ##EQU3## where η is the orientational viscosityand P is the magnitude of the ferroelectric polarization density. Thepolarization typically derives from the type of chiral tail used, whilethe viscosity is a function of the core and chiral tail. The first FLCcompound to be characterized was DOBAMBC, which contains abenzylideneaminocinnamyl core, a n-decyloxy achiral tail and2-methylbutyloxy chiral tail. As shown in Table 1, pure DOBAMBC exhibitsa smectic C* phase with a ferroelectric polarization of -3 nC/cm².

There are a number of reports of compounds containing phenylbenzoate,biphenylbenzoate, tolane, diphenyldiacetylene and related cores coupledto 1-methylalkyloxy or lactate chiral tail units which possessmonotropic smectic C* phases affording useful switching properties inthe Clark-Lagerwaal SSFLC light valve, or which can be employed as FLCdopants to induce high polarization, fast switching speeds, high tiltangle, high birefringence, or other useful properties when combined inmixtures with FLC host materials.

The following are exemplary reports of such FLC compounds:

Furukawa, K. et al. (1988) Ferroelectrics 85:451-459 refers to chiralsmectic C compounds having an ester group in the core and an opticallyactive tail group, either alkoxy or alkoxy carbonyl, with anelectronegative substituent, either halogen or cyano group, ortho to thechiral tail, for example: ##STR5## where m=2, X=H, Halogen or CN.

Walba, et. al. (1991) Ferroelectrics 113:21-36 and Walba and Otterholm,U.S. Pat. No. 5,145,601 refers to FLC components possessing the1-methylheptyloxy chiral tail unit in combination with pyridine andpyridine-N-oxide core units, where the nitrogen atom of the pyridinering is adjacent to the point of attachment of the chiral tail, withformula: ##STR6## where X=an electron lone pair or oxygen.

It has been demonstrated in Walba, et. al., (1989) J. Am. Chem. Soc.111:8273-8274 and U.S. Pat. No. 5,138,010 that for some side-chainferroelectric liquid crystal polymers composed of a polymer backbonesubstituted with mesogenic units wherein the achiral tail provides theconnection between the polymer backbone and the mesogenic units, themesogenic unit in the polymer imparts ferroelectric ppolarizationsimilarly to the low molar mass mesogen itself, though the switchingspeeds and alignment properties of such polymers are different than thelow molar mass mesogens, the switching speeds generally being slower. Anexemplary FLC side chain polymer has formula: ##STR7##

Kapitza et al., (1990) Adv. Mater. 2:539-543 have disclosed side chainFLC siloxane polymers and copolymers of formula: ##STR8##

While a number of FLCs (both pure compounds and mixtures) useful in theClark-Lagerwaal device geometry and other related devices involvinglarge nuclear motions in response to applied fields have been reported,there has been very little work aimed at creating FLCs for electronicNLO applications. Indeed, it has been commonly known in the art of NLOmaterials design that FLCs are not useful in applications where themedium must respond strongly and quickly to applied fields (eitherrespond to DC or low frequency fields in times less than 10 nsec, orrespond to AC fields with frequencies larger than 100 MHz). Suchapplications require response with small or no nuclear motions. Forexample, SHG requires response of the material to optical frequency ACapplied fields, at which frequencies the molecular nuclei cannotrespond.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide new classes of LCand FLC compounds with large X.sup.(2). The present invention providesFLC compounds and/or components of the formula: ##STR9## where Z iseither an electron donor or acceptor, and cannot be H, where X is H, adonor, or acceptor grouping, and when Z is an acceptor, X is H or is adonor, and when Z is a donor, X is H or an acceptor,

where j=0, or j=1 and A is 0, (NR₁), (O₂ C), (CO), (CO₂), (N(R₁)CO), or(CON(R₁)) and R₁ =H, or small alkyl,

where p=0, or p=1,

where k=0, or k=1 and (B) is (O₂ C), (CO₂), (N(R₂)CO), (CON(R₂)), (C=N)or (N=C), and R₂ =H or small alkyl,

where l=0, or l=from 1 to 4 and (D) is (C═C), (C═N), (N═C), (N═N) or(C═C), and when l≠0, then (B) ≠CO₂ or (CON(R₂),

where the Rigid Core is a liquid crystal core unit, including but notlimited to 1,4-phenylene, 4,4'-biphenyl and substituted aryl rings suchas phenylbenzoate rings, an aromatic heterocyclic ring or rings andsubstituted rings such as phenylpyridines and phenylpyrimidines,1,4-disubstituted cyclohexyl, [2,2,2]-bicyclooctane ring or rings,[1,1,1]-bicyclopentane ring or rings, cubane ring or rings, or anycombination of such ring or rings,

and where R' is a straight chain or branched alkyl or monoalkene grouphaving from 1 to 20 carbon atoms which can be chiral or achiral, and R*is a chiral grouping. For use as liquid crystal materials, R', which isan alkyl group or mono alkenyl group, preferably contains 5 to 12 carbonatoms, and where one or more of the non-neighboring carbon atoms in R'can be O, S, or Si(CH₃)₂, and R* is a chiral grouping which affords corecoupling such that the functional array (Z-Ar-X) is oriented in a polarfashion in the FLC phase, close to the polar axis of the FLC phase.

where (Y)_(p) R* is ((Y)_(n) C*H(CH₃)R) where p=0, or p=1 and Y is O,NR₃, or (CO), where R₃ is H or small alkyl, where the tetrahedralstereocenter indicated by the asterisk is enriched in one configuration,and where R is a straight chain or branched alkyl having from 2 to 15carbon atoms and where one or more of the nc neighboring carbon atoms inR can be O, S, or Si(CH₃)₂, or where is (CO₂ R₄) where R₄ is methyl oran alkyl with from 2 to 13 carbon atoms and where one or more of thenon-neighboring carbon atoms in R₄ can be O, S, or Si(CH₃)₂, or

where is (Y)_(p) R* is ((Y)_(p) CH₂ C*HFC*HFR), where P=1, Y is O--NR₅,where R₅ is H or small alkyl, R is a straight chain or branched alkylhaving from 2 to about 11 carbon atoms and where one or more of thenon-neighboring carbon atoms in R can be O, S, or Si(CH₃)₂ and where theindicated stereocenters considered together are enriched in either the(S), (S) or (R), (R) configurations.

The acceptor groupings useful for X and Z include any grouping known inthe art to be an electron acceptor (for example, any grouping causingdeactivation of an aromatic ring relative to benzene in an electrophilicaromatic substitution reaction), which includes halogen, (CN), (COR),(CO₂ R), (CON(R)₂), (SO₂ R'), and (NO₂) where R is H or small alkyl, andR' is small alkyl. It is known in the art that for obtaining largemolecular β the NO₂ grouping is preferred to halogen or (CN). Inaddition, the (SO₂ CF₂ R) grouping, where R is alkyl, is a preferredacceptor, and the tricyanovinyl grouping (C(CN)=C(CN)₂) is a preferredacceptor. For ferroelectric liquid crystals, the NO₂ and (SO₂ CF₃) arepreferred. Furthermore, the (NHCOCH₃) grouping can be an acceptor if thelone pair on nitrogen is unable to interact with the aromatic ring in aresonance sense.

The donor groupings useful for X and Z include any grouping known in theart to be an electron donor (for example any grouping causing activationof an aromatic ring relative to benzene in an electrophilic aromaticsubstitution reaction), which includes (OR), (N(R)₂), (N(R)CO(R')),(OCOR), where R and R' are H or small alkyl, or other atom lesselectronegative than halogen and where the atom connected to thearomatic ring possesses a lone pair able to interact with the aromaticring in a resonance sense.

When Z is an acceptor grouping, then when p=1, Y=O or NR₃ is preferred.When Z is a donor grouping, then when p=1, Y=(CO) is preferred.

Preferred D is (C═C) and preferred B are CO₂, O₂ C except that if l≠O,then B≠CO₂.

The present invention also provides FLC compounds and/or components ofthe formula: ##STR10## Where Z, X, B and D are as defined above, where Qand T are both H; T is H or an electron donor when Q is an electronacceptor or T is H or an electron acceptor when Q is an electron donor;

where R₂ must be a chiral R' group or R* and R₁ can be R' or R* where R'and R* are as defined above;

when R₁ =R₂, then Z and Q are either both donors or both acceptors, andT and X are independently H or an acceptor when Q and Z are donors, or Hand a donor when Q and Z are acceptors, and

when both R₁ and R₂ are chiral, but R₁ ≠R₂, and R₁ and R₂ both impartthe same sign of P when used individually, then Z and Q are either bothdonors or both acceptors, and T and X are independently H or an acceptorwhen. Q and Z are donors, and T is H or a donor when Q and Z areacceptors, or when both R₁ and R₂ are chiral, R₁ ≠R₂ and R₁ and R₂afford opposite sign of P when used individually, then Z is a donor whenQ is an acceptor, and Z is an acceptor when Q is a donor, and T is H oran acceptor when Q is a donor, and T is H or a donor when Q is anacceptor, and X is H or an acceptor when Z is a donor, and X is H or adonor when T is an acceptor, and

where m=0 or 1 and g=0 or 1, and

where E and F are defined as D and B above, respectively, and where hcan be 0 or 1 to 4 and m can be 0 or 1 to 4 independently, and where iand k can be 0 or 1, independently.

Preferably h+l≦4, k=0 when l≠0, i=0 when h≠0, l=0 when k=1, and h=0 wheni=1. More preferably, k and h =1 while i and m are both 0 or i and m =1while both k and h=0.

The rigid core is preferably a 1,4-phenylene ##STR11## or a4,4'biphenylene ##STR12## Preferably the numbers of rings in thecompound is 3 or 4.

In a specific embodiment, this invention provides chiral, nonracemiccompounds of formula I: ##STR13## where k=0 or 1, when k=1, B=COO; n andm, independently of one another are 0 or 1;

R₁ and R₂ are an OR_(a), --COOR_(b) or an R* group such that at leastone of R₁ or R₂ is an R* group wherein:

R_(a) is a straight-chain or branched alkyl or monoalkene group havingfrom 2 to 16 carbon atoms;

R_(b) is a straight-chain or branched alkyl or monoalkene group havingfrom 2 to 15 carbon atoms;

R* is a chiral nonracemic tail group selected from the group consistingof OC*H(CH₃)R_(c), O--C*H(CH₃)COOR_(d) and OCH₂ C*HFC*HFR_(e) in whichthe * indicates an asymmetric carbon enriched in one stereoconfigurationwhich for OCH₂ C*HFC*HFR_(e) is either the (S,S) or (R,R)stereoconfiguration and wherein:

R_(c) is a straight-chain or branched alkyl or monoalkene group havingfrom two to fifteen carbon atoms, R_(d) is a straight-chain or branchedalkyl or monoalkene group having from 2 to 13 carbon atoms and R_(e) isa straight-chain or branched alkyl or monoalkene group having from 2 to11 carbon atoms and wherein for each of R_(a), R_(b), R_(c), R_(d),R_(e) one or more of the non-neighboring carbon atoms, except anyunsaturated carbon atoms, can be substituted with an O, S, or Si(CH₃)₂group; and

X₁, X₂, X₃,l and X₄ are either H, an electron donor or an electronacceptor; such that when X₁ is an acceptor, X₃ is either H or a donorand when X₁ is a donor, X₃ is either H or an acceptor, and when X₂ is anacceptor, X₄ is either H or a donor and when X₂ is a donor, X₄ is eitherH or an acceptor and such that when R₂ is R*, X₁ cannot be H and when R₁is R* X₂ cannot be H.

In a more specific embodiment, this invention provides chiral,nonracemic o-nitroakoxyaromatic compounds of formula I:

wherein n=0 or 1, m=0 or 1, X₁ is an NO₂ grouping, X₂, X₃ and X₄ are H,R₂ is a chiral nonracemic group, and R₁ is an alkyl group having from 5to 15 carbon atoms;

or wherein n=0 or 1, m=0 or 1, X₂ is NO₂, X₁, X₃ and X₄ are H, R₁ is achiral nonracemic group, and R₂ is an alkyl group having from 6 to 12carbon atoms;

or wherein n=0 or 1, m=0, X₁ is NO₂, X₃ is NR'R", X₂ and X4 are H, R₂ isa chiral nonracemic group, and R₁ is an alkyl group having from 6 to 12carbon atoms, and where R' is H or CH₃, and R" is H, CH₃, or (COCH₃);

or wherein n=0 or 1, m=0 or 1, X₁ and X₂ are NO₂ groups, X₃ and X₄ areH, R₁ is a chiral nonracemic group, and R₂ is a chiral non-racemicgroup;

or wherein n=0, m=0 or 1, X₄ is NO₂, X₁ is NR'R", X₁ and X₃ are H, R₁ isa chiral nonracemic group, and R₂ is an alkyl group having from 6 to 12carbon atoms, and where R' is H or CH₃, and R" is H, CH₃ or NHCOCH₃ (butR" is NHCOCH₃ only when R' is not H);

or wherein n=0, m=0 or 1, X₂ is NH₂, X₄ is NHCOCH₃, X₁ and X₃ are H, R₁is a chiral nonracemic group, and R₂ is an alkyl group having from 6 to12 carbon atoms.

Also provided is the m-nitroalkoxyaromatic compound of formula I whereinn=0 or 1, m=0, X₃ is NO₂, X₁, X₂ and X₄ are H, R₂ is a chiral nonracemicgroup, and R₁ is an alkyl group having from 6 to 12 carbon atoms, andthe m-nitroalkoxyaromatic compound of formula I wherein n=0, m=0 or 1,X₄ is NO₂, X₁, X₂, and X₃ are H, R₁ is a chiral nonracemic group, and R₂is an alkyl group having from 6 to 12 carbon atoms. These compound areprovided as a test and control compounds. While such compounds,specifically where X₁ is H when R₂ is chiral, and where X₂ is H when R₁is chiral, and where only one chiral tail is present, are not expectedto possess large X.sup.(2), they are useful as, for example, FLC hostmaterials or components of FLC mixtures.

In a further embodiment, this invention provides chiral, nonracemiccompounds with tolane cores of formula II: ##STR14## where q=1 or 2, andwhere R₁ and R₂ are an OR_(a), --COOR_(b) or an R* group such that atleast one of R₁ or R2 is an R* group wherein:

R_(a) is a straight-chain or branched alkyl or monoalkene group havingfrom 2 to 16 carbon atoms;

R_(b) is a straight-chain or branched alkyl or monoalkene group havingfrom 2 to 15 carbon atoms;

R* is a chiral nonracemic tail group selected from the group consistingof OC*H(CH₃)R_(c), O--C*H(CH₃)COOR_(d) and OCH₂ C*HFC*HFR_(e) in whichthe * indicates an asymmetric carbon enriched in one stereoconfigurationwhich for OCH₂ C*HFC*HFR_(e) is either the (S,S) or (R,R)stereoconfiguration and wherein:

R_(c) is a straight-chain or branched alkyl or monoalkene group havingfrom two to fifteen carbon atoms, R_(d) is a straight-chain or branchedalkyl or monoalkene group having from 2 to 13 carbon atoms and R_(e) isa straight-chain or branched alkyl or monoalkene group having from 2 to11 carbon atoms and wherein for each of R_(a), R_(b), R_(c), R_(d),R_(e) one or more of the non-neighboring carbon atoms, except anyunsaturated carbon atoms, can be substituted with an O, S, or Si(CH₃)₂group; and

X₁, X₂, X₃, and X₄ are either H, an electron donor or an electronacceptor; such that when X₁ is an acceptor, X₃ is either H or a donorand when X₁ is a donor, X₃ is either H or an acceptor, and when X₂ is anacceptor, X₄ is either H or a donor and when X₂ is a donor, X₄ is eitherH or an acceptor and such that when R₂ is R*, X₁ cannot be H and when R₁is R* X₂ cannot be H.

In a more specific embodiment, this invention provides chiral,nonracemic lactate esters with tolane cores of formula II:

wherein X₁ is NO₂, X₂ and X₃ are H, R₂ is a chiral nonracemic group andR₁ is an alkoxy group with from 6 to 12 carbon atoms, and q=1 or 2;

wherein X₁ is NO₂, and X₃ is NR'R" R₂ is a chiral nonracemic group, andR₁ is an alkyl group having from 6 to 12 carbon atoms, and where R₁ is Hor CH₃, and R" is H, CH₃, or (COCH₃), and;

wherein X₃ is NO₂ and X₁ is NR'R'', R₂ is a chiral nonracemic group, andR₁ is an alkyl group having from 6 to 12 carbon atoms, and where R' is Hor CH₃, and R" is H, CH₃, or (COCH₃); and wherein X₁ and X₂ are NO₂, X₃is H, q=2, and R₁ and R₂ are both chiral nonracemic groups and are boththe same group.

Also provided is the compound of formula II wherein X₁ and X₃ are H, R₂is a chiral nonracemic group, and R₁ is an alkyl group with from 6 to 12carbon atoms. While such compounds, specifically where X₁ is H when R₂is chiral, and where X₂ is H when R₁ is chiral, and where only onechiral tail is present, are not expected to possess large X.sup.(2),they are useful as, for example, FLC host materials or components of FLCmixtures.

Specifically, the present invention provides compounds of formula II:##STR15## where Z, X, B, D, E, F, Q, T, R₁, R₂, and g, h, i, k, l and mare defined as above.

Particularly useful for obtaining large X.sup.(2) are compounds offormula IV in which one or both of Z or Q is a NO₂ group. Preferredcompounds of formula 1 are those in which E and D can be --C═EC-- and Band F can be CO₂ or O₂ C except that B≠CO₂ when l≠0 and F≠O₂ C when h≠0.##STR16## where Z'=NO₂ and Q' can be H or NO₂ ; R₂ * must be a chiralgroup either R* or a chiral R' group and R₁ can be a chiral or nonchiralR' group. It is preferred that if R₁ O is a chiral group that Q' is NO₂.

Preferred chiral nonracemic groups R₁ or R₂ are those which afford ahigh degree of core coupling, as described in U.S. patent applicationSer. No. 542,838, when ortho substituents are present. Such chiral tailsgenerally cause an increase in ferroelectric polarization when one orthosubstituent is electronegative relative to the same structure where bothortho substituents are H. That is, the ferroelectric polarization ofcompounds of formulas I-IV would be larger when X₁ is NO₂ or otherelectronegative substituent and X₂ and X₃ are H, than when X₁ is H andX₂ and X₃ are H. Such chiral tails include the nonracemic1-methylalkyloxy grouping (R=(CH(CH₃)C_(x) H_(2x+1))), where x isgreater than 1, and where the 1-methylheptyloxy grouping (x=6) is morepreferred, and the nonracemic 1-methylcarbonyloxy grouping(R=(CH(CH₃)CO₂ C_(x) H_(2x+1))) where x is an alkyl group with from 1 to10 carbon atoms. In general, the groups C_(x) H_(2x+1) in both of thesetails can also have one or more stereocenters, and can also possessheteroatom substituents at stereocenters or at non-stereogenic carbonatoms, and where non-neighboring carbon atoms can be replaced by S, O orSi(CH₃)₂.

In general, the compounds of the present invention are useful ascomponents of liquid crystal materials. In particular, chirallyasymmetric molecules of this invention are useful as components offerroelectric liquid crystal materials. Certain of these compounds canimpart high X.sup.(2) to ferroelectric liquid crystals, either as purecompounds or as components of mixtures. Certain of the compounds in thisinvention can be employed as FLC host materials. Certain of thecompounds of this invention exhibit liquid crystal phases, includingsmectic C phases.

DETAILED DESCRIPTION OF THE INVENTION

The compounds of the present invention can be prepared by a variety oftechniques known in the art. In particular, compounds of formula B and Ccan be prepared by those of ordinary skill in the art employingtechniques will known in the art and following the procedures providedhereinafter. Some details of the present invention have been providedin: Walba, D. M., et al. (1991) ACS Symp Ser #455:484. Walba et al.,(1991) Mol. Cryst. Liq. Cryst. 198:51.

The general synthesis of chiral and achiral compounds of formula Ihaving k=1, R₁ and R2 alkoxy, and X₁ =NO₂, n=0 or 1, and m=0, isillustrated in Scheme I. The hydroxyl group of biphenol (1) is protectedas the acetate by treatment with acetic anhydride in pyridine to give 2.Acetate 2 is functionalized in the p' position by Friedel-Craftsacylation using oxalyl chloride/AlCl₃ to give the p' acid chloride,which is hydrolyzed to the acid in an aqueous workup. This acid is thentreated with hydroxide to deprotect the phenolic hydroxyl grouping,affording 3. Alkylation of the phenolic hydroxyl grouping of 3 isaccomplished by Williamson etherification to give 4, which is thenconverted to acid chloride 5 by treatment with oxalyl chloride inbenzene/DMF.

Phenol 11 is prepared as follows. Monobenzone (6) is acylated withbenzoyl chloride to give phenylbenzoate 7. Removal of the benzylgrouping by hydrogenation using Pd/C catalyst gives the phenol 8.Nitration of 8 is accomplished with the sodium nitrate/lanthanum nitratereagent, affording o-nitrophenol 9, which is then coupled with R₂ OH togive the ether 10 using the stereospecific Mitsunobu reaction. TheMitsunobu coupling proceeds with inversion of configuration at thestereocenter of alcohol R₂ OH in the case where R₂ is a chiralnonracemic group. Deprotection of the phenolic hydroxyl grouping bytreatment of 10 with hydroxide affords phenol 11.

Coupling of acid chloride 5 with phenol 11 then gives the compounds offormula I, wherein X₁ is NO₂, n=1, and m=0. Alternatively, coupling of ap-alkyloxy benzoic acid chloride 12 with phenol 11 gives the compoundsof formula I, wherein X₁ is NO₂, n=0, and m=0.

The general synthesis of chiral and achiral compounds of formula Ihaving R₁ and R₂ alkoxy, and where X₁ =NO₂, n=0 or 1, and m=1, isillustrated in Scheme II. Biphenol (13) is protected as the mono-benzoylester 14 by treatment with benzoyl chloride in pyridine. The phenol ringof compound 14 is then selectively nitrated using either lanthanumnitrate with nitric acid and HCl, or with nitric acid in acetic acid.The sodium nitrate-lanthanum nitrate conditions are less preferred.Nitrophenol 14 is then coupled with R₂ OH using the stereospecificMitsunobu coupling procedure to give 16 wherein the stereocenter of R2OHis inverted. Deprotection of the phenol by hydrolysis of the benzoateester with hydroxide ion then gives 17. Coupling of phenol 17 with etheracid chloride 5 or acid chloride 12 then gives the compounds of formulaI wherein n=0 or 1, m=1, and X₁ is NO₂.

The general synthesis of chiral and achiral compounds of formula Ihaving R₁ and R₂ alkoxy, and where X₃ =NO₂, n=0 or 1, and m=0, isillustrated in Scheme III. Coupling of R₂ OH with monobenzone (6) givesether 18 with inversion of configuration at the stereocenter of R₂ OH.Deprotection of the phenolic hydroxyl grouping of 18 is accomplishedusing hydrogenation, which gives phenol 19. Nitration of 19 using thesodium nitrate-lanthanum nitrate conditions then gives phenol 20, whichis coupled with either acid chloride 12 or acid chloride 5 to give thecompounds of formula I wherein X₃ is NO₂, m=0, and n=0 or 1.

The general synthesis of chiral and achiral compounds of formula Ihaving R₂ alkoxy and R₁ alkoxy or (OCH(CH₃)CO₂ R), and where X₂ is NO₂,n=0, and m=0 or 1, is illustrated in Scheme IV. The carboxyl grouping of4-hyrdroxy-3-nitrobenzoic acid (22) is protected as the methyl ester togive 22. The alcohol R₁ OH is then coupled stereospecifically to thephenolic hydroxyl of 22 to give the ether 23 using the Mitsunobucoupling. The Mitsunobu coupling proceeds with inversion ofconfiguration at the stereocenter of alcohol R₁ OH in the case where R₂is a chiral nonracemic group wherein the stereocenter is on the carbonbearing the OH group. Hydrolysis of ester 23 with hydroxide ion thengives the acid 24 which is converted to acid chloride 25 by treatmentwith thionyl chloride. Alternatively, the ester deprotection step caninvolve treatment of methyl ester 23 with trimethylsilyl iodide. Thelatter method is preferred with R₁ is (OCH(CH₃)CO₂ R).

Coupling of the acid chloride 25 with either the alkoxy phenol 26 or 27,prepared by mono-etherification of diphenol 13, or from monobenzone (6)by alkylation then debenzylation, respectively, then affords thecompounds of formula I where X₂ is NO₂, n=0, and m=0 or 1.

The general synthesis of chiral and achiral compounds of formula Ihaving R₂ alkoxy and R₁ alkoxy or (OCH(CH₃)CO₂ R), and where X₂ is NO₂,n=1, and m=0 or 1, is illustrated in Scheme V. Protection of thecarboxyl grouping of p'-hydroxy-biphenylbenzoic acid (3) as the methylester gives phenol 28. Nitration of phenol 28 with sodiumnitrate-lanthanum nitrate and HCl gives the nitro phenol 29, which iscoupled with R1OH using the stereospecific Mitsunobu coupling reaction.Deprotection of the resulting ester 30 using hydroxide or trimethylsilyliodide, which is preferred when R₂ is (CH(CH₃)CO₂ R), gives acid 31.Coupling of acid 31 with either phenol 26 or phenol 27 then gives thecompounds of formula I where X₂ is NO₂, n=1, and m=0 or 1.

The general synthesis of chiral and achiral compounds of formula Ihaving R₁ and R2 are alkoxy, and where X₄ is NO₂, n=0, and m=0 or 1, isillustrated in Scheme VI. Coupling of RtOH with 4-hydroxy-2-nitrotoluene(33) using the Mitsunobu coupling reaction gives ether 34 with inversionof configuration at the stereocenter of R₁ OH if the stereocenter is thecarbon bearing the OH group or R₁ OH. Bromination of the methyl group of34 then gives bromide 35, which is converted to aldehyde 36 by treatmentof with silver nitrate, then treatment of the resulting nitrate esterwith hydroxide. Oxidation of aldehyde 36 gives acid 37, which isconverted to acid chloride 38 with oxalyl chloride in benzene/DMF.Coupling of acid chloride 38 with either phenol 26 or phenol 27 thengives the compounds of formula I wherein n=0, m=0 or 1, and X₄ is NO₂.

The general synthesis of chiral and achiral compounds of formula Ihaving R₁ =R₂ ' and R₂ and R₂ ' are alkoxy, and where X₃ 1 and X₂ areNO₂, n=0 or 1, and m=0 or 1, is illustrated in Scheme VII. Coupling ofeither phenol 11 or phenol X17 with either acid chloride 25 or acidchloride 32 using NaH in THF solvent gives the compounds of formula Iwherein n is 0 or 1, m is 0 or 1, X₁ and X₂ l are NO₂, and R₂ and R₂ 'are both chiral tails, not necessarily the same, but both affording thesame sign of P when used individually.

Compounds of formula V can be employed as LC or FLC host materials.##STR17##

The general synthesis of chiral and achiral compounds of formula Vhaving R₁ and R₂ alkyl, is illustrated in Scheme VIII. Coupling of R₂ OHwith phenol 14 using the Mitsunobu coupling reaction gives ester 39.When R₂ is a chiral group with the hydroxyl-bearing carbon astereocenter, the product is produced with inversion of configuration atthe stereocenter of R₂. Treatment of ester 39 with hydroxide ion givesphenol 40, which is nitrated using the sodium nitrate-lanthanumnitrate-HCl conditions to give nitrophenol 41. Coupling of this phenolwith acid chloride 12 using NaH then gives the compounds of formula V.

The general synthesis of chiral and achiral compounds of formula Ihaving R₁ and R2 alkoxy, and where X₁ and X₃ are not H, and n=0 or 1,and m=0, and where X₂ and X₄ are not H, and n=0, and m=0 or 1, proceedthrough the common aldehyde intermediates 49. The general synthesis ofaldehyde intermediates 49 is shown in Scheme IX. Nitration ofp-methylacetophenone gives the nitrotoluene derivative 43. Reduction ofthe nitro group to an amino group with stannous chloride followed byacylation with acetyl chloride/pyridine then gives the amide 44.Baeyer-Villiger oxidation of 44 with mCPBA gives the acetate 45. Theester grouping of 45 is selectively hydrolyzed with hydroxide ion togive phenol 46, which is nitrated to nitrophenol 47 using nitric acidwith acetic acid/acetic anhydride. Coupling of 47 with R₁ OH or R₂ OHusing the Mitsunobu coupling reaction then gives the toluene derivative48. When this ROH is chiral, with a stereocenter at the carbon bearingthe hydroxyl grouping, then 48 is formed with inversion of configurationat the stereocenter. Oxidation of the methyl group of 48 to givealdehdye 49 is accomplished by treatment of 48 with ceric ammoniumnitrate in acetic acid/water.

The general synthesis of chiral and achiral compounds of formula Ihaving R₁ and R₂ alkoxy, and where X₁ and X₃ are not H, and n=0 or 1,and m=0, is shown in Scheme X. Baeyer-Villiger oxidation of aldehyde 49(where the R group is R₂) using mCPBA gives the phenol 50 via anintermediate formate ester which is not isolated. Phenol 50 is coupledwith either acid 51 or acid 4 using dicyclohexylcarbodiimide andp-dimethylaminopyridine to give the compounds of formula I where X₁ isNO₂, X₃ is NHAc, n=0 or 1, and m=0. Selective hydrolysis of the amidegrouping of I where X₃ is NHAc using HCl in acetone then gives thecompounds of formula I where X₁ is NO₂, X₃ is NH₂, n=0 or 1, and m=0.

The general synthesis of chiral and achiral compounds of formula Ihaving R₁ and R₂ alkoxy, and where X₂ and X₄ are not H, and n=0, and m=0or 1, is shown in Scheme XI. Oxidation of aldehyde 49 (where the R groupis R₁) with permanganate gives the acid 52, which is coupled with eitherphenol 26 or phenol 27 to give compounds 53 with m=0 or 1. The spectralproperties of compounds 53 (specifically the fact that these compoundsare not absorbing in the visible part of the spectrum and are white)show that in this particular functional group array, the acetamide group(NHAc) is not a donor group. Reduction of the nitro group of 53 givesthe amines I, X₂ =NH₂, X₄ =NHAc, m=0 or 1. The fact that these aminesare absorbing in the visible part of the spectrum and are yellow showsthat in this particular functional array the NHAc group is acting as anacceptor and the NH₂ group is acting as a donor.

Selective hydrolysis of the amide group of 53 using HCl in aqueousacetone gives compounds of formula I where X₂ =NO₂, X₄ =NH₂, m=0 or 1and n=0. In this case the nitro group is acting as an acceptor and theamino group is acting as a donor.

The general synthesis of chiral and achiral compounds of formula IIhaving R₁ alkoxy or (OCH(CH₃)CO₂ R) and R₂ alkoxy or (OCH(CH₃)CO₂ R),and where X₁ is NO₂, and q=1 is shown in Scheme XII. Coupling ofp-iodophenol (54) with R₁ OH using the Mitsunobu coupling reaction givesiodo ether 56. Metal catalyzed coupling of iodide 56 with the acetoneadduct of acetylene, followed by deprotection of the terminal acetylenewith acid then gives acetylenic ether 59.

Coupling of 54 with R₂ OH using the Mitsunobu conditions gives ether 58,while nitration of 54 gives the nitrophenol 55. Coupling of 55 with R₂OH under.Mitsunobu conditions gives nitro ether 57. Coupling of either57 or 58 with acetylene 59 using a metal catalyst gives the compounds offormula II where X₁ is NO₂ or H, and n=1.

The general synthesis of chiral and achiral compounds of formula IIhaving R₁ alkoxy or (OCH(CH₃)CO₂ R) and R₂ alkoxy or (OCH(CH₃)CO₂ R),and where X₁ and X₂ are NO₂, and q=2 is shown in Scheme XIII. Couplingof iodoether 57 with the acetone adduct of acetylene using a metalcatalyst, followed by deprotection of the terminal acetylene with acidgives acetylene 60. Dimerization of 60 using a copper catalyst in thepresence of oxygen then gives the compounds of formula II where X₁ andX₂ are NO₂, and q=2.

The general synthesis of chiral and achiral compounds of formula III andIV is outlined in Scheme XIV. Coupling of the p-iodophenol (54) withTMS-acetylene gives the phenol-substituted acetylene (61). Acid chloride12 (Scheme 11) or 25 (Scheme IV) is reacted 61 to give a phenylbenzoateacetylene 62. Finally, coupling of iodoethers like 57 or 58 to 62 givesthe benzoate tolane IV where Q' and Z' are H or NO₂.

The starting materials for synthesis of compounds of formulas I-V by theprocedures of Schemes I-XIV are readily available either as commercialproducts or by synthetic routes that are well known in the art. Forexample, alkoxy substituted phenols are either available from commercialsources or are readily prepared by known methods (see Neubert et al.(1978) Mol. Cryst. Liq. Cryst. 44:197-210). Introduction of achiraltails wherein non-alternate carbon atoms are replaced by heteroatoms,including oxygen or silicon, is generally discussed in: Hemmerling, W.et al., (1989) European Patent No. 0355,008. ##STR18##

                  TABLE 2                                                         ______________________________________                                        Compound of formula I where R.sub.1 = OC.sub.10 H.sub.21, R.sub.2 =           (S)--(OCH(CH.sub.3)C.sub.6 H.sub.11, X.sub.1 = NO.sub.2, X.sub.2 =            X.sub.3 = X.sub.4 = H, k = 1, m = 0 and n = 1 (W 314)                         X←33.6°--C*←93.7°--A←119.1°--I            X--80°→C*                                                       P/sinθ = -611 @ T-Tc = -10°                                      Compound of formula I where R.sub.2 = OC.sub.10 H.sub.21, R.sub.1 =           (S)--(OCH(CH.sub.3)C.sub.6 H.sub.11, X.sub.2 = NO.sub.2, X.sub.1,             X.sub.3 = X.sub.4 = H, k = 1, m = 1 and n = 0 (W 313)                         X←55°--E←64.8°--C*←94.2°→A.rarw    .90.5°--I                                                              X--65°→E--84°→C*                                  P/sinθ = -494 @ T-Tc = -10°                                      Compound of formula I where R.sub.1 = (S)--(OCH(CH.sub.3)C.sub.6 H.sub.11,    R.sub.2 = (S)--(OCH(CH.sub.3)C.sub.6 H.sub.11, X.sub.1 =                      X.sub.2 =NO.sub.2, X.sub.3 = X.sub.4 = H, n = 0, k = 1, and m = 1 (W          319)                                                                          For a 20% mixture in W 82                                                     X←15.5°--C*←57.5°--I                                  P.sub.ext @ T-Tc = -10° = -119                                         P.sub.ext @ T-Tc = -42° = -402                                         P.sub.ext /sinθ = -271 @ T-Tc = -10°                             Compound of formula I where R.sub.1 = (OC.sub.10 H.sub.21, R.sub.2 =          (S)--(OCH(CH.sub.3)C.sub.6 H.sub.11, X.sub.3 = NO.sub.2, X.sub.1,             X.sub.2 and X.sub.4 = H, k = 0, m = 0 and n = 1 (W 320)                       X←50°--C*←62.9°--N*←67.4°--I              P.sub.ext /sinθ = -130 @ T-Tc = -10°                             Compound of formula I where R.sub.2 = (OC.sub.10 H.sub.21, R.sub.1 =          (S)--(OCH(CH.sub.3)C.sub.6 H.sub.11, X.sub.2 = NO.sub.2, X.sub.1 =            X.sub.3 = X.sub.4 = H, n = 1, k = 1, and m = 0 (W 316)                        X←17.5°--C*←60.5°--A←89.1°--I             P.sub.ext /sinθ = -330 @ T-Tc = -10°                             Compound of the formula I where R.sub.2 = (S)--(OCH(CH.sub.3)C.sub.6          H.sub.11                                                                      R.sub.1 = OC.sub.10 H.sub.21, X.sub.1 = NO.sub.2, X.sub.2 = X.sub.3 =         X.sub.4 = H, k = 1, n = 0 and m = 1 (W 317)                                   X←23.5°--A←76.5°--I                                   X--41°→A--76.5→I                                         Compound of formula II where R.sub.1 = OC.sub.10 H.sub.21, R.sub.2 =          (R)--(OCH(CH.sub.3)CO.sub.2 C.sub.2 H.sub.5, X.sub.1 = NO.sub.2               X.sub.2 = X.sub.3 = H, and q = 1 (W 334)                                      For a 10% mixture in MDW 158                                                  X←23°--C*←60.5°--A←67.5°--I               P.sub.ext @ T-Tc = -10° = +79.4                                        P.sub.ext @ T-Tc = -35.5° = +199                                       P.sub.ext /sinθ = +238 @ T-Tc = -10°                             Compound of formula II where R.sub.1 = OC.sub.10 H.sub.21, R.sub.2 =          (R)--(OCH(CH.sub.3)CO.sub.2 C.sub.2 H.sub.5, X.sub.1 =                        X.sub.2 = X.sub.3 = H, and q = 1 (W 336)                                      For a 10% mixture in MDW 158                                                  X←20°--C*←56.6°--A*←64.3°--N*←66.    8°--I                                                                  P.sub.ext @ T-Tc = -10° = +63                                          P.sub.ext @ T-Tc = -31.6° = +100                                       P.sub.ext /sinθ = +164 @ T-Tc = -10°                             Compound of formula II where R.sub.1 = OC.sub.10 H.sub.21, R.sub.2 =          (R)--(OCH(CH.sub.3)CO.sub.2 C.sub.2 H.sub.5, X.sub.1 =                        X.sub.2 = X.sub.3 = H, and q = 1 (W 336)                                      For a 10% mixture in MDW 158                                                  X←20°--C*←56.6°--A*←64.3°--N*←66.    8°--I                                                                  P.sub.ext @ T-Tc = -10° = +63                                          P.sub.ext @ T-Tc = -31.6° = +100                                       P.sub.ext /sinθ = +164 @ T-Tc = -10°                             The 1:1 mixture of W 316 and W 317                                            X←<rt--C*←45°--A*←79°--I                         X←<rt→C*                                                          P.sub.ext @ T-Tc = -23° = -222                                         P.sub.ext /sinθ = -545 @ T-Tc = -23°                             Compound of formula II where R.sub.1 = OC.sub.10 H.sub.21, R.sub.2 =          (R)--(OCH(CH.sub.3)CO.sub.2 C.sub.2 H.sub.5, X.sub.1 =                        NO.sub.2, X.sub.2 = X.sub.3 = H, and q = 1 (W 334)                            For a 10% mixture in ZLI 3234B                                                X←<10°--C*←53.7°--A*←68.8°--N*←85    °--I                                                                   P.sub.ext @ T-Tc = -10° = +112                                         P.sub.ext @ T-Tc = -43.7° = +203                                       P.sub.ext /sinθ = +362 @ T-Tc = -10°                             Compound of formula I where R.sub.2 = OC.sub.10 H.sub.21, R.sub.1 =           (S)--(OCH(CH.sub.3)C.sub.6 H.sub.11, X.sub.2 = NO.sub.2,                      X.sub.4 = NH.sub.2, X.sub.1 = X.sub.3 = H. k = 1,                             m = 1 and n = 0 (W 341)                                                       For a 5% mixture in MDW 158                                                   X←<6°--C*←70.5°--N*←75°--I                P.sub.ext @ T-Tc = -10° = -141                                         P.sub.ext @ T-Tc = -40.5° = -202                                       P.sub.ext /sinθ = -310 @ T-Tc = -10°                             The 1:1 mixture of W 314 and W 317                                            X←<rt--C*←51°--A*←97°--I                         P.sub.ext @ T-Tc = -29° = -272                                         P.sub.ext /sinθ = -610 @ T-Tc = -29°                             ______________________________________                                    

Table 2 summarizes phase sequences, polarization densities and tiltangles of some exemplary FLC compounds of formula I, and phasesequences, polarization densities and tilt angles of some exemplary FLCmixtures containing exemplary compounds of formulas I and II. In Table2, the phases are noted as X=crystal, I=isotropic liquid, A=smectic A,C*=chiral smectic C, and phase transition temperatures are given in ° C.Also, names such as W 314 are given to the compounds in Table 2 foreasier reference.

Polarization densities (P) are given in nC/cm² and the magnitude of Pwas measured by integration of the dynamic current response to a surfacestabilized ferroelectric liquid crystal cell on reversing the appliedelectric field using a slight modification of the standard methods ofMartinot-Lagarde (1976) J. Phys. Colloq. (Orsay, Fr.) 37:129 andMartinot-Lagarde (1977) J. Phys. Lett. (Orsay, Fr.) 38:L-17. Thepolarization reversal current was measured after applying a triangularwave form (±15 volts) across a 2.5 μm (using polyimide spacers) polymeraligned (DuPont Elvamide 8061) SSFLC cell (Patel, J. S. et al. (1986) J.Appl. Phys. 59:2355; Flatischler, K. et al., (1985) Mol. Cryst. Liq.Cryst. 131:21; Patel, J. S. et al. (1984) Ferroelectrics 57:137) withindium-tin oxide (ITO) conducting glass electrodes. The signal (currentv. time) was digitized using a Sony-Tektronix 390AD programmabledigitizer. The current waveform showed a peak characteristic of thepolarization reversal; this current peak was integrated. Division of thevalue of this integration (charge) by the active area of the cellafforded the magnitude of the ferroelectric polarization. For allmeasurements, the diameter of the ITO coated area of the cell was 0.50inch. The sign of the polarization was determined directly fromobservation of molecular orientation in SSFLC cells upon application ofelectric fields.

The optical tilt angle was determined by rotating the shear or polymeraligned cell until extinction was obtained. The polarity of the cell wasreversed and the cell was rotated by a measured angle to obtainextinction again. The angle by which the cell was rotated is equal to2Θ. The tilt angle was obtained by dividing this angle by two. Tiltangles and polarizations were measured as a function of temperature, andthe data are shown in graphical form in PCT application US 92/03427. Forcomparison purposes, the values of the normalized polarization (P/sinΘat T-T_(c) =-10° C., where T_(c) is the temperature of the transitioninto the C* phase from a higher temperature) or the normalizedextrapolated polarization (P_(ext) /sinΘ where P_(ext) is theextrapolated polarization of the compound obtained by measuring thepolarization of a mixture with a known C or C* host, and assuming thatthe polarization is linear with concentration of the components) arealso given in Table 2.

In some of the measurements on mixtures, the smectic C materialsW82=4'-(n-decyloxy)phenyl-4-(4(S)-methylhexyloxy) benzote, MDW158=racemic W 82, and ZLI 3234B (an achiral smectic C host materialobtained from E. Merk, Darmstadt (see Geelhaar, T. (1988) Ferroelectrics85:329-349) were used as hosts. W 82 is known to possess anenantiotropic ferroelectric C* phase with a very low polarizationdensity of the order of -1 nC/cm². MDW158 and ZLI 3234B are racemic andachiral C phases, respectively, and therefore possess zero polarization.Mixtures of the compounds of the present invention (guests) with thesehosts possess polarization density deriving primarily or exclusivelyfrom the guest component. Extrapolated polarizations were calculatedassuming a linear relationship between polarization and concentration ofthe components. It is understood that this extrapolation is notrigorous, and that the extrapolated values are only approximate.

Finally, the X.sup.(2) of two of the compounds of formula I as measuredby the SHG method are also given in Table 2. The data were obtainedusing the method of type 1 eeo angle phase matched second harmonicgeneration from 1,064 nm Nd:YAG laser light, combined with Maker fringeexperiments and a computational curve-fitting technique to extract theindividual components of the d tensor. The application of type 1 eeoangle phase matched SHG to ferroelectric liquid Crystals (including ZLI3654; see Table 1) is reported in: Taguchi (1989) supra. Thedetermination of the individual d-tensor coefficients for aferroelectric liquid crystal (SCE 9; see Table 1) by this method isdescribed in: Liu (1990) supra.

Referring to the data in Table 2, it should be noted that several of thecompounds of formula I possess broad monotropic and in some casesenantiotropic smectic C, liquid crystal phases. Thus achiral or racemicmaterials of this type are useful as FLC host materials.

It is an important feature of the present invention that the compoundsof formulas I and II where X₁ and/or X₂ are NO₂, and R₂ and/or R₁,respectively, are chiral nonracemic core-coupling tails, possess largeferroelectric polarization density. For example, the compound of formulaI wherein X₁ =NO₂, X₂ =X₃ =X₄ =H, R₁ =OC₁₀ H₂₁, R₂ =((S)--OCH(CH₃)C₆H₁₃, k=1, m=0, and n=1, also known as W 314, shows a polarizationdensity of -556 nC/cm² at 34° C. To our knowledge this is the highestpolarization density reported to date for an FLC with one chiral tail.This is important in the present invention since the functional grouparray for this compound providing the large B axis oriented along thepolar axis also possesses a large nearly colinear permanent moleculardipole moment. Specifically, this functional group array is theo-nitroalkoxy unit, similar to that present in the parent o-nitroanisoleas illustrated below. ##STR19##

The dipole moment of o-nitroanisole is reported to be 4.8D (McClellan,A. L. (1963) Tables of Experimental Dipole Moments; W.H. Freeman andCompany: San Francisco). The observed ferroelectric polarization densityof W 314, expressed in units of D/molecule, and assuming a density ofabout 0.8 gms/cm³, is P_(W314) =-2.1 D/molecule. Thus, making thereasonable assumption that the nitroalkoxy unit is responsible for theobserved polarization, we can see that about 40% of the dipole of themolecules is actually oriented along the polar axis in the FLC phase ofW 314. It should be noted that this is much better (by at least a factorof 2) than could be achieved for the same functional array and the samenumber density of nitroalkoxy units using the poled polymer method.

The large observed polarization density Of the FLC phase of W 314,coupled with the fact that the NLO active unit has a large moleculardipole moment, leads to the conclusion that the NLO active units of W314 are indeed well aligned along the polar axis in the FLC phase. Thisis consistent with the NLO results obtained for W 314 as shown in Table3. Note that the second harmonic intensity at the top of the anglephase-matched peak is 8×10⁴ times that of DOBAMBC, and that themagnitudes of the largest coefficients of the d tensor are in factlarger than that for KDP (see Table 1), even though the data were takenat an elevated temperature of 60° C., where the polar order (asevidenced by the ferroelectric polarization density) is considerablesmaller than at 34° C. To our knowledge this compound possesses thelargest X.sup.(2) measured for any ferroelectric liquid crystal.

                                      TABLE 3                                     __________________________________________________________________________    Values of the ferroelectric polarization, SHG efficiency, and X.sup.(2)       (d.sub.eff and                                                                d coefficients), for FLCs of the present invention.                                                   SHG       d                                           Entry              P    arb  d.sub.eff                                                                          coefficients                                number                                                                             compound      (nC/cm.sup.2)                                                                      units*                                                                             (pm/V)                                                                             (pm/V)                                      __________________________________________________________________________    1    W 314         -420†                                                                       8 × 10.sup.4                                                                 0.23 d.sub.2,3 = 0.63 ± 0.03                       The compound of              d.sub.2,2 = 0.6 ± 0.3                         formula I where R.sub.1 =    d.sub.2,1 = 0.08 ± 0.02                       n-C.sub.10 H.sub.21, R.sub.2 =                                                                             d.sub.2,5 = 0.16 ± 0.05                       (S)--(CH(CH.sub.3)C.sub.6 H.sub.11,                                           X.sub.1 = NO.sub.2, X.sub.2 = X.sub.3 =                                       X.sub.4 = H, m = 0 and n = 1                                             2    W 316         -246 2 × 10.sup.4                                                                 0.1                                                   Compound of formula I                                                         where R.sub.2 = n-C.sub.10 H.sub.21,                                          R.sub.1 = (S)--(CH(CH.sub.3)C.sub.6 H.sub.11,                                 X.sub.2 = NO.sub.2, X.sub.1 = X.sub.3 =                                       X.sub.4 = H, n = 1 and m = 0                                             __________________________________________________________________________     *Intensity of the second harmonic light at the top of the type 1 eeo angl     phasematched peak.                                                            †The SHG measurements with W 314 were performed at 60° C.,      where P ≅ -420 nC/cm.sup.2.                                    

                                      TABLE 4                                     __________________________________________________________________________     ##STR20##                                                                    W335, X.sub.1 =H, X.sub.2 =H, R.sub.1 =n-C.sub.10 H.sub.21                                                W333, X.sub.1 =NO.sub.2, X.sub.2 =H, R.sub.1                                  =n-C.sub.10 H.sub.21                              MX511, 10% (wt) W335 in MDW158                                                                            MX542, 10% (wt) W333 in W346                      X←21.2--C*←64.2--A*←68--N*←70--I                                                      X←<31--C*←67--A*←107--I            X→C*--74→N*--77→I                                                                    X-- →C*--68→A*--107→I        P.sub.ext =-46nC/cm.sup.2 @ 25° C., T-Tc=-39° C.,               θ=23.5°        P.sub.ext =-290nC/cm.sup.2 @ 25° C.,                                   T-Tc=-43° C., θ=28°           P.sub.ext =-37nC/cm.sup.2 @ 55° C., T-Tc=-10° C.,               θ=18.5°        P.sub.ext =-180nC/cm.sup.2 @ 55° C.,                                   T-Tc=-10° C., θ=18.3°          ##STR21##                                                                                                 ##STR22##                                        MX546, 16% (wt) W355 in W346                                                                              X←<32--C*←55.5--A*←113--I          X←23--C*←69--A*←105.8--1                                                                   X--57→A*--114→I                     P.sub.ext =-160nC/cm.sup.2 @ 24° C., T-Tc=-45° C.,              θ=29°          P.sub.ext =-250nC/cm.sup.2 @ 25° C.,                                   T-Tc=-30.5° C., θ=27.5°       P.sub.ext =-94nC/cm.sup.2 @ 60° C., T-Tc=-10° C.,               θ=22.5°        P.sub.ext =-200nC/cm.sup.2 @ 45° C.,                                   T-Tc=-10° C., θ=26°           __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________     ##STR23##                                                                    W355, Z'=H, Q'=H, R.sub.1 =n-C.sub.10 H.sub.21                                                            MX549, 50% (wt) W349 in W346                      X←S.sub.? ←61--C*←79--N*←114--I                                                       X←25--C*←45.7--A*←105.5--I         X--61→C*--75→N*--114--I                                                                     X--36→C*                                   P=-27nC/cm.sup.2 @ 65° C., T-Tc=-14° C., θ=26.5.degree    .                           P.sub.ext =-95nC/cm.sup.2 @ 10° C.,                                    T-Tc=-35.7° C., θ=14°         P=-27nC/cm.sup.2 @ 69° C., T-Tc=-10° C., θ=26.5.degree    .                           P.sub.ext =-57nC/cm.sup.2 @ 35° C.,                                    T-Tc=-10° C., θ=11°           W349, Z'=NO.sub.2, Q'=H, R.sub.1 =n-C.sub.10 H.sub.21                                                     MX556, 20% (wt) W349 in [75% W346/25%                                         MDW158]                                           X--36→A*--80→1                                                                              X←<14--C*←62--A*←105--I            X←SB←5--A*←80--I                                                                           X--<14→C*--62→A*--107→I      MX541, 10% (wt) W349 in W346                                                                              P.sub.ext =-200nC/cm.sup.2 @ 15° C.,                                   T-Tc=-47° C., θ=25°           X←29--C*←80.5←120--I                                                                       P.sub.ext =-133nC/cm.sup.2 @ 50° C.,                                   T-Tc=-10° C., θ=16.5°         X--36→C*                                                                ##STR24##                                                                                                 ##STR25##                                                                    Liquid at room temperature, no apparent LC                                    phases down to -20° C.                     MX548, 25% (wt) W349 in W346                                                                              MX550, 10% (wt) W349 in W346                      X←<25--C*←74.9--A*←115--I                                                                  X←23--C*←69--A*←106--I             X--36→C*             X→30→C*                             P.sub.ext =-280nC/cm.sup.2 @ 20° C., T-Tc=-54.9° C.,            θ=28°          P.sub.ext =-720nC/cm.sup.2 @ 25° C.,                                   T-Tc=-44° C., θ=30.5°         P.sub.ext =-190nC/cm.sup.2 @ 20° C., T-Tc=-10° C.,              θ=23.5°        P.sub.ext =-460nC/cm.sup.2 @ 60° C.,                                   T-Tc=-10° C., θ=24.5°         __________________________________________________________________________

While the individual components of the d tensor have not yet beenmeasured, angle phase-matched SHG from the compound of formula I whereinX₂ =NO₂, X₁ =X₃ =X₄ =H, R₁ =((S)--CH(CH₃)C₆ H₁₃, R₂ =C₁₀ H₂₁, n=1 andm=0, also known as W 316, is also large relative to previously known FLCmaterials as shown in Table 3.

The polarization density observed for the compound of formula I where X₁=H, X₃ =NO₂, X₂ and X₄ =H, R₁ =OC₁₀ H₂₁, and R₂ =(S)--(O(CH(CH₃)C₆ H₁₃,k=1, m=0, and n=1 (W 320) exhibits the same polarization expected forthe compound where all the X groups are H (Furukawa (1988) supra, Walba(1991) supra). Similarly, the compound of formula II where where R₁=OC₁₀ H₂₁, R₂ =((R)--(OCH(CH₃)CO₂ C₂ H₅), X₁ =NO₂, X₂ =X₃ =H, and n=1 (W334) shows a considerably larger extrapolated polarization in two hoststhan the compound of formula II where R₁ =OC₁₀ H₂₁, R₂=((R)--(OCH(CH₃)CO₂ C₂ H₅), X₁ =X₂ =X₃ =H, and n=1 (W 336).

Also provided is the compound of formula I where R₂ =(S)--(OCH(CH₃)C₆H₁₁), R₁ =OC₁₀ H₂₁, X₁ =NO₂, X₂ =X₃ =X₄ =H, k=1, n=0 and m=1 (W 317).This compound possesses a broad temperature smectic A phase, but nosmectic C, phase. It is known that chiral smectic A LC materials exhibitthe electroclinic effect (Garoff, S., et al., (1977) Phys. Rev. Lett.38:848) and that the electroclinic effect can be useful for electroopticdevice applications of the type involving nuclear motions (Andersson,G., et al., (1987) Appl. Phys. Lett. 51:640). The compound of thepresent invention (W 317) exhibits a surprisingly large, relativelytemperature independent electroclinic effect far from the virtualsmectic C*-smectic A transition. When R₁ =ω-decenyloxy, theelectroclinic effect of the W 317 alkene is approximately half as large.

Finally, two mixtures containing only components of formula I, andpossessing room temperature C* phases, including one mixture with anenantiotropic room temperature C, phase (1:1 W316 and W 317) areprovided. This illustrates the general fact that when LC components withimmiscible crystal phases but miscible LC phases are mixed, then thetemperature range of the LC phases are broadened. This technique canproduce stable room temperature FLC mixtures composed entirely of thecompounds of the present invention. The mixtures wherein W317 is acomponent, in particular the 1:1 mixture of W316 and W317, also exhibitsa large electroclinic effect in the smectic A phase.

The FLC properties of the compounds of formula II are illustrated by theproperties of the compounds and mixtures listed in Table 4.

The FLC properties of the compounds of formula IV are illustrated by theproperties of the compounds and mixtures listed in Table 5. Ofparticular interest is the high polarization room temperature smectic C,mixture MX556 of W349 in a 3:1 (by weight) mixture of W346 with MDW158.W346 is racemic W314. Also of interest is W350 which has a very highextrapolated polarization density.

Although not wishing to be bound by any theory, it is believed that theproperties of the compounds of the present invention may bequalitatively understood and interpreted in terms of the diagrams shownin Schemes XV-XVIII. These diagrams assume that in the smectic C phasethe "crystal packing" forces exerted on an individual molecule by therest of the molecules in the phase may be approximated by a binding sitetaking the shape of a bent cylinder (see Walba, D.M., et al., (1986) J.Am. Chem. Soc. 108:5210-5221 and Walba (1991) supra). The functionalgroup orientation occurring in the phase may be considered to resultfrom the way the molecules "dock" into this binding site. The diagramsafford a qualitative estimate of how the molecules are oriented relativeto the C* phase tilt plane when docked in a preferred way in the bindingsite. In order to make this estimate, a judgment concerning thepreferred conformations present in the phase, and how theseconformations dock into the binding site must be made. For many FLCstructural types, it is possible to make educated guesses as to thesepreferred conformations and their docking mode. Such educated guesseswere used to construct the diagrams shown in the schemes.

Scheme XV illustrates the suggested origins of the ferroelectricpolarization of compounds of formula I wherein X₁ -X₄ are H, R.sub. 2 is(S)--OCH(CH₃)C₆ H₁₃, k=1 and m=0. That is, the polarization derives froman excess of molecules occurring in orientation A relative toorientations B or C. In orientation A, the molecular dipole moment fromthe Ar-O-C.sub.α functional group is oriented along the polar axis(normal to the tilt plane) in such a way that negative P is predicted (Pis opposed to z× n). If orientation C were favored, the positive P wouldbe expected. If orientation B were favored, then small P would beexpected since the dipole component oriented normal to the tilt plane issmall. Conformation A should be favored by simple conformationalanalysis arguments (i.e., the methyl group should prefer to be anti tothe methylene group at C.sub.γ of the tail and the orientation shownrelative to the tilt plane comes from the preferred mode of docking inthe binding site.

Scheme XVI illustrates the suggested origins of the ferroelectricpolarization and X.sup.(2) of compounds of formula I wherein X₁ =NO₂, X₂-X₄ are H, R₂ is (S)--OCH(CH₃)C₆ H₁₃, k=1 and m=0. When one positionortho to the alkoxy tail is occupied by a nitro grouping and the otherortho position bears a hydrogen atom, the preferred conformation A nowhas two different possible orientations of the nitro group relative tothe tilt plane. Due to a clear excess steric hindrance present inconformation A", it is suggested that conformation A' is preferred. Inthis conformation and orientation, the molecular dipole moment and themolecular B from the nitro alkoxy unit are oriented along the polar axisof the phase. An enhanced ferroelectric polarization relative to thecompounds without the ortho nitro grouping is expected, as well asenhanced X.sup.(2).

In the case where the nitro grouping is meta to the alkoxy tail, as forexample in the compound of formula I W320, no enhancement in thepolarization or X.sup.(2) relative to compounds without a nitroSubstituent is expected. This can be seen by inspection of the diagramsin Scheme XVII. In this case the conformations A' and A" are expected tobe close in energy, and to have almost equal number densities in thephase. Therefore, the nitroalkoxy grouping of this molecule is notexpected to be oriented in a polar fashion relative to the tilt plane,and most or all of the polarization and X.sup.(2) of the moleculederives simply from the alkoxy grouping in the chiral tail.

Scheme XVIII illustrates the binding site model for orientation of theprototypical 37 large β" functional array, the p-nitroaniline unit,along the polar axis in FLC phases of compounds of formula I where X₁=NO₂, X₃ =NH₂, X₂ and X₄ are H, R₂ is (S)--OCH(CH₃)C₆ H₁₃, k=1 and m=0(diagram on the left), and where X₂ =NO₂, X₄ =NH₂, X₁ and X₃ are H, R₁is (S)--OCH(CH₃)C₆ H₁₃, k=1 and n=0 (diagram on the right). In thelatter case, it is possible that the indicated intramolecular hydrogenbonding is also occurring between the carbonyl oxygen of the group(B)=COO, and one of the hydrogens on the nitrogen atom, leading toadditional polar orientation of the carbonyl grouping as indicated.

These same arguments can be made for other core coupling chiral tails.Variation in the structure, length and degree of branching of the R₁ andR₂ groups of compound encompassed in formulas I and II can affect theliquid crystal properties of the pure material or mixtures containingthem. For example, some of the chiral nonracemic compound of the presentinvention may possess smectic C* phases while others do not and thecharacteristics of any such smectic C* phases (i.e., stability,temperature range) may vary. ##STR26##

The following examples illustrate the invention and are in no wayintended to limit the scope of the invention. In particular, it will beapparent to those of ordinary skill in the art that when attached to apolymeric backbone to give side-chain LC homopolymers or copolymers, themesogenic units of the present invention may give FLC polymers with LCproperties similar to the low molar mass mesogens of the presentinvention. In addition, such FLC polymers will, upon cooling, givecrystalline, microcrystalline, or glassy polymer solids (Walba (1989)supra) with stable polar order which are of particular utility incertain NLO applications requiring a solid thin film material. It iswithin the skill of an ordinary artisan to prepare FLC polymers, suchpolysiloxanes, employing the compounds of the present invention, inparticular the compounds wherein the achiral tail is an ω-alkenyl tail.It will be understood by those in the art that enantiomers will haveequal magnitude but opposite sign of the ferroelectric polarization, andthat such enantiomers are of similar utility for NLO applications andare encompased by this invention. This invention also encompassesmixtures of the compounds of the present invention with themselves orwith any compatible hosts.

All references cited in this specification are hereby incorporated byreference in their entirety.

EXAMPLES Example 1 Synthesis of (S)-4-(1-methylhepytloxy)-3-nitrophenol(compound 11 of scheme I, R₂ =(S)--OCH(CH₃) C₆ H₁₃) (S)-[4-(1-methylheptyloxy)-3-nitrophenyl]-benzoate

To an argon-flushed flask containing 8 mmol of nitro-phenol 9 (Scheme I)(literature: Rajamohan, K. et al., (1973) Indian J. Chem. 11 1076) and1.25 eq. of triphenylphosphine dissolved 150 ml of dry THF, a solutionof 8.08 mmol of (R)-2-octanol in 20 ml of dry THF was added via syringe.Then 1.25 eq. of diethyl azodicarboxylate dissolved in 40 ml of dry THFwas added dropwise over 30 min. The reaction mixture was heated to 60°C. and stirred at this temperature for 19-22 h. Water (5 drops) wasadded and stirring was continued for another hour. The reaction mixturewas evaporated and the crude product was extracted with a hexanes/ethylacetate (70/30) and filtered through a short pad of silica gel. Thefiltrate was evaporated and the ether-derivative was purified by flashchromatography on silica gel to give (S)-[4-(1-methylheptyloxy)-3-nitrophenyl]-benzoate (Compound 10, Scheme I,R₂ =(S)--OCH(CH₃)C₆ H₁₃) in 80-90% yield as a yellow liquid: R_(f)[hexanes/ethyl acetate 85/15]: 0.52; ¹ H-NMR (300 MHz, CDCl₃): δ0.82 (t,3H, J=6.8 Hz); 1.15-1.52(m, 8H); 1.35(d, 1H, J=6.1 Hz); 1.62(m, 1H);1.78(m, 1H); 4.48(m, 1H); 7.09(d, 1H, J=9 Hz); 7.37(dd, 1H, J=2.8 Hz,J=9 Hz); 7.46-7.67(m, 3H); 7.70(d, 1H, J=2.8 Hz); 8.16(dd, 2H, J=2.1 Hz,J =7.2 Hz); ¹³ C-NMR (300 MHz, CDCl₃): δ14.00, 19.45, 22.50, 25.18,29.10, 31.66, 36.16, 76.94, 116.44, 119.12, 127.25, 128.71, 128.77,130.24, 134.02, 140.44, 142.79, 149.57, 164.96; IR (CHCl₃): 3040, 2940,2850, 1740, 1600, 1525, 1490, 1305, 1260, 1190, 1060, 1025, 900, 825cm⁻¹ ; Mass spectrum, m/z(rel.intensity): 371 (M⁺ 0.2), 259(3), 213(4),184(14), 105(100), 77(15), 55(10), 43(19), 41(11).

Anal. Calcd. for C₂₁ H₂₅ NO₅ : C 67.91, H 6.78, N 3.77. Found: C68.22, H6.90, N3.99.

(S)-4-(1-methylheptyloxy)-3-nitro-phenol

To a solution of 5.3 mmol of ester 10 in 40 ml of methanol and 15 ml ofwater, 22 mmol of LiOH.H₂ O was added. The reaction mixture was stirredvigorously at room temperature for 14-22 h until no starting materialwas detected by TLC. The solution was diluted with 65 ml of 3.5% (wt/wt)NaOH solution, acidified by adding concentrated HCl with ice andextracted several times with ethyl ether. The combined organic layerswere dried over anhydrous MgSO₄ and the solvent removed. The phenol werepurified by flash chromatography with hexanes/ethyl acetate [90:10]togive (S)-4-(1-methyl-heptyloxy)-3-nitro-phenol (Compound 11, Scheme I,R₂ =(S)--OCH(CH₃)C₆ H₁₃) in 89-98% yield as an orange liquid: R_(f)[hexanes/ethyl acetate 85/15]: 0.24; ¹ H NMR (300 MHz, CDCl₃): δ0.84(t,3H, J=6.8 Hz), 1.16-1.48(m, 8H), 1.27(d, 3H, J=6.1 Hz), 1.56(m, 1H),1.72(m, 1H), 4.35(m, 1H), 5.44(broad s, 1H), 6.94(d, 1H, J=9 Hz),7.01(dd, 1H, J=2.8 Hz, J=9 Hz), 7.28(d, 1H, J=2.8 Hz); ¹³ C NMR (300MHz, CDCl₃): δ13.98, 19.49, 22.50, 25.19, 29.15, 31.66, 36.19, 77.57,112.03, 118.50, 121.44, 140.98, 145.81, 148.84; Mass spectrum, m/z (rel.intensity): 267 (M⁺ 0.3), 156 (8), 155(100), 71(9) 57(20), 55(16),43(29).

Anal. Calcd. for C₁₄ H₂₁ NO₄ : C 62.90, H 7.92, N 5.24. Found: C 62.82,H 8.05, N 5.24.

Example 2 Synthesis of(S)-4'-(1-methylheptyloxy)-3'-nitro-4-hydroxybiphenyl (Compound 17,Scheme II, R₂ =(S)--OCH(CH₃)C₆ H₁₃) 4'-Hydroxy-4-biphenylyl-benzoate

To a solution of 100 mmol of biphenol in 120 ml of dry pyridine wasadded 1.5 eq. of benzoyl chloride dropwise over 45 min. The reactionmixture was stirred for another 45 min at room temperature and then 20ml of ethanol was added and stirring was continued for 30 min. Themixture was poured into water-ice and stirred for 30 min. Theprecipitate was filtered and washed several times with water. Theproduct phenol was purified by flash chromatography on silica gel withdichloromethane as eluent. Recrystallization from toluene afforded4'-hydroxy-4-biphenylyl-benzoate (Compound 14, Scheme II, R₂ =(S) --OCH(CH₃) C₆ H₁₃) as a white solid in 22% yield: R_(f) [dichloromethane]:0.25; ¹ H NMR (300 MHz, Acetone-d₆): δ7.95(d, 2H, J=8.8 Hz), 7.34(d, 2H,J=8.5 Hz), 7.50-7.80(m, 7H), 8.21(dd, 2H, J=1.2 Hz J=8.3 Hz), 8.64(broads, 1H); ¹³ C NMR (300 MHz, Acetone-d₆): δ116.60, 123.02, 128.12, 128.90,129.69, 130.62, 130.78, 132.33, 134.61, 139.65, 150.94, 158.14, 165.64;Mass spectrum, m/z(rel.intensity): 290(M⁺ 16), 105(100), 77(29).

Anal. Calcd. for C₁₉ H₁₄ O₃ : C 78.61, H 4.86. Found: C 79.02, H 4.80.

4'-Hydroxy-3'-nitro-4-biphenylyl benzoate

To an argon-flushed flask containing a suspension 0.486 g (1.68 mmol) of4'-hydroxy-4-biphenylyl benzoate in 10 ml of acetic acid at 10°-15° C.,0.345 ml of HNO₃ (d: 1.41) was added dropwise (about a drop per min).Then the reaction mixture was vigorously stirred at the same temperaturefor 30 min. Water (40 ml ) was added and the mixture was again stirredfor 30 min. The yellow precipitate was filtered, washed several timeswith water, dried and purified by flash chromatography on silica gelusing dichloromethane/hexanes [65/35] as eluent to give4'-hydroxy-3'-nitro-4-biphenylyl benzoate (compound 15, Scheme II) as ayellow solid (0:539 g, 96%). This material was recrystallized fromethanol to give product of mp. 163° C.; R_(f) [hexanes/dichloromethane40/60]: 0.42; ¹ H NMR (300 MHz, CDCl₃): δ7.25(d, 1H, J=8.7 Hz), 7.33(d,2H, J=8.7 Hz), 7.50-7.70(m, 5H), 7.84(dd, 1H, J=2.7 Hz, J=8.7 Hz), 8.23(d, 2H, J=7.2 Hz), 8.32(d, 1H, J=2.7 Hz), 10.60(s, 1H); ¹³ C NMR (300MHz, CDCl₃): δ120.54, 122.45, 122.81, 127.85, 128.65, 129.33, 130.23,133.04, 133.78 136.04, 136.22, 150.91, 154.44, 165.15; IR (CHCL₃):3250(broad), 3020, 1740, 1620, 1540, 1510, 1490, 1325, 1270, 1225, 1220,1170, 1080, 1065, 1025, 1000, 850 cm⁻¹ ; Mass spectrum,m/z(rel.intensity): 335(M⁺ 7), 105(100), 77(16).

Anal. Calcd. for C19H₁₃ NO₅ : C 68.06, H 3.91, N 4.18. Found: C 68.11, H3.84, N 4.03.

S -4'-1-methylheptloxy)-3'-nitro-4-biphenylbenzoate

4'-Hydroxy-3'nitro-4-biphenylyl benzoate was alkylated using the sameprocedure as that used to prepare(S)-[4-(1-methylheptyloxy)-3-nitrophenyl]-benzoate to give(S)-4'-(1-methyl-heptyloxy)-3'- nitro-4-biphenylylbenzoate (Compound 16,Scheme II, R₂ =(S) --OCH(CH₃) C₆ H₁₃) as a slightly yellow solid; (mp.39° C.). R_(f) [toluene/hexanes 70/30]: 0.27; ¹ H NMR(300 MHz, CDCl₃);δ0.87(t, 3H, J=6.7 Hz), 1.20-1.55(m, 8H), 1.36(d, 3H, J=6.1 Hz), 1.65(m,1H), 1.80(m1H), 4.53(m, 1H), 7.11(d1H, J=8.8 Hz), 7.28(d, 2H, J=8.7 Hz),7.46-7.65(m, 5H), 7.68(dd, 1H, J=2.4 Hz, J=8.8 Hz), 7.98 (d, 1H, J=2.4Hz), 8.21(dd, 2H, J=1.5 Hz, J=7.2 Hz); ¹³ C NMR (300 MHz, CDCl₃);δ13.99, 19.48, 22.50 25.16, 29.11, 31.66, 36.17, 76.51, 116.10, 122.34,123.77, 127.81, 128.63, 129.33, 130.21, 131.95, 132.46, 193.75, 136.35,141.07, 150.69, 165.18; Mass spectrum, m/z(rel.intensity): 447(M⁺ 5),417(12), 416(9), 335(16), 305(13), 105(100), 77(8), 71(12), 57(18),55(10), 43(30).

Anal. Calcd. for C₂₇ H₂₉ NO₅ : C 72.46, H 6.53, N 3.13. Found: C72.46, H6.55, N 3.10.

(S)-4'-(1-methylheptloxy)-3'-nitro-4-hydroxybiphenyl

The benzoyl ester of(S)-4'-(1-methylheptyloxy)-3'-nitro-4-biphenylylbenzoate was saponifiedusing the same procedure as that used for saponification of(S)-[4-(1-methylheptyloxy)-3-nitrophenyl]-benzoate except that thereaction was carried out at 60° C. to give(S)-4'-(1-methylheptyloxy)-3'-nitro-4-hydroxybiphenyl (Compound 17,Scheme II, R₂ =(S)--OCH(CH₃)C₆ H₁₃) as a very viscous orange liquidafter flash chromatography with hexanes/ethyl acetate [88/12]; R_(f)[hexanes/ethyl acetate 85/15]: 0.17; ¹ H NMR (300 MHz, CDCl₃): δ0.86(t,3H, J=6.6 Hz), 1.18-1.52(m, 8H), 1.35(d, 3H, J =6.1 Hz), 1.62(m, 1H),1.78(m, 1H), 4.50 (m, 1H), 5.22(broad s, 1H), 6.89(d, 2H, J=8.5 Hz),7.07 (d, 1H, J=8.8 Hz), 7.39 (d, 2H, J=8.5 Hz), 7.62(dd, 1H, J =2.4 Hz,J=8.8 Hz), 7.92 (d, 1H, J=2.4 Hz); ¹³ C NMR (300 MHz, CDCl₃): δ13.99,19.49, 22.50, 25.19, 29.10, 31.65, 36.17, 76.57, 115.94, 116.17, 123.30,127.99, 131.21, 131.64, 133.09, 141.00, 15.42, 155.52; IR (CHCl₃); 350,3300(broad), 3020, 2920, 2840, 1610, 1540, 1510, 1485, 1350, 1260, 1220,1160, 1110, 1040, 925, 825 cm⁻¹ ; Mass spectrum, m/z(rel.intensity):343(M⁺ 5), 231(100), 185(6), 57(6), 43(12).

Anal. Calcd. for C₂₀ H₂₅ NO4: C 69.95, H 7.34, N 4.08. Found: C 69.84, H7.44, N 4.08.

Example 3 Synthesis of (S)-4(1-methyl-heptyloxy)-2-nitro-phenol(Compound 20, Scheme III, R₂ =(S)--OCH(CH₃)C₆ H₁₃)(S)-p-Benzyloxy-(1-methylheptyloxy)benzene

To an argon-flushed flask containing a solution of 3.01 g (15 mmol) ofp-benzyloxy-phenol and 1.25 eq of triphenylphosphine in 220 ml in drydichloromethane, was added a solution of 4.91 g (15.14 mmol) of(R)-2-octanol in 30 ml of dry dichloromethane via syringe. Then 1.20 eqof diethyl azodicarboxylate dissolved in 60 ml of dry dichloromethanewas added dropwise for 30 min. The reaction mixture was stirred at roomtemperature for 19 h, Then 5 drops of water were added and the mixturewas stirred for 1 h. The solvent was then evaporated and the residualcrude product was triturated in a mixture of hexanes/ethyl acetate[70/30] for 1 h and filtered through a short silica gel pad. Thefiltrate was evaporated and the product was purified by flashchromatography on silica gel using dichloromethane/hexanes [10/90 ] aseluent, affording 3.32 g (71%) of(S)-p-Benzyloxy-(1-methylheptyloxy)benzene (Compound 18, Scheme III, R₂=(S)-OCH(CH₃) C₆ H₁₃) as a colorless liquid: R_(f)[dichloromethane/hexanes 10/90]: 0.13; ¹ H NMR (300 MHz, CDCl₃):δ0.87(t, 3H, J=6.6 Hz), 1.20-1.60(m, 12H), 1.70(m, 1H), 4.21(m, 1H),5.00(s, 2H), Distorted AA'BB' System [6.82(d, 2H) 6.88(d, 2H)],7.30-7.46(m, 5H); ¹³ C NMR (300 MHz, CDCl₃): δ14.02, 19.77, 22.55,25.52, 29.26, 31.77, 36.51, 70.63, 74.95, 115.77, 117.35, 127.49,127.87, 128.55, 137.39, 152.53, 153.01; IR (CHCl₃): 3010, 2940, 2850,1600, 1500, 1475, 1450, 1375; 1230, 1200, 1125, 1025, 925, 825 cm⁻¹ ;Mass spectrum, m/z (rel. Intensity): 312(M⁺ 7), 212(15), 91(100), 71(5),57(8), 43(10).

(S)-p-(1-methylheptyloxy)phenol

A flask fitted with a gas inlet tube was charged with a suspension of10% Pd/C (6 g) in 100 ml of dry dichloromethane. The flask was evacuatedand filled with argon, then evacuated again and filled with hydrogen,which was then allowing to bubble through the stirred suspension for 30min before a solution of 30 mmol of benzyl ether in 70 ml of drydichloromethane was added via syringe. After the reaction was judgedcomplete by TLC (about 4 h) hydrogen ebullition was stopped, and theresulting suspension was filtered through a Celite pad. The solvent wasevaporated and the resulting crude product was purified by flashchromatography on silica gel (hexanes/ethyl acetate [99/1]) to give(S)-p-(1-methylheptyloxy)phenol (Compound 19, Scheme III, R₂ =(S)--OCH(CH₃) C₆ H₁₃) as a colorless liquid in 85-97% yield: R_(f)[hexanes/ethyl acetate 95/5]: 0.15. [α]_(D) ²⁵ :+11.5° (c 3.31, CHCl₃)(Literature value =+11.4° (c 10.1, CHCl₃): Inukai, T. et. al., (1986)Mol. Cryst. Liq. Cryst. 141:251); ¹ H NMR (300 MHz, CDCl₃): δ0.87 (t,3H, J =6.3 Hz), 1.15-1.56 (m, 9H), 1.23 (d, 3H, J=6.1 Hz), 1.70(m, 1H),4.17(m, 1H), 5.28(s, 1H), Distorted AA'BB'System [6.72(d,2H) 6.76(d,2H)]; ¹³ C NMR (300 MHz, CDCl₃): δ14.00, 19.72, 22.52, 25.49, 29.22,31.74, 36.43, 75.55, 116.08, 117.85, 149.64, 152.12; IR (CHCl₃): 3600,3480(broad), 3010, 2940, 2850, 1600, 1500, 1450, 1375, 1225, 1170, 1120,1030, 925, 825 cm⁻¹ ; Mass spectrum, m/z (rel.intensity): 222(M⁺ 5),110(100), 43(7).

(S)-4(1-methylheptyloxy)-2-nitro-phenol

To an argon-flushed flask containing 85 mg (1 mmol) of NANO₃, 4.3 mg(0.01 mmol) of La(NO₃)₃.6 H₂ O, 1.2 ml of water and 0.8 ml of HCl, wasadded a solution of 222 mg (1 mmol) of (S)-4-(1-methylheptyloxy)-phenolin 6 ml of ethyl ether. After 4 h 30 min of vigorous stirring at roomtemperature the reaction mixture took on a yellow color that changedvery fast to orange. After turning orange, the mixture was stirred foranother 15-20 min and then water was added. The organic layer wasseparated and the aqueous layer was extracted several times with water.The combined organic layers were washed with water until the washes werepH ˜6 and then with brine. The resulting organic solution was dried andthe solvent evaporated. Flash chromatography on silica gel withhexanes/ethyl acetate [99/1] (other eluents were used with the sameresults) afforded a mixture of two compounds that could be purified byflash chromatography on alumina [activity grade III, 6% of water] usingCl₄ C →Cl₄ C/Cl₂ CH₂ [80/20] as eluent. The first fractions afforded 130mg (50%) of (S)-4-(1-methyl-heptyloxy)-2-nitrophenol (Compound 20,Scheme III, R₂ =(S)--OCH(CH₃)C₆ H₁₃) as an orange liquid; R_(f)[toluene/hexanes 45/55]: 0.45; ¹ H NMR (300 MHz, CDCl₃): δ0.86(t, 3H,J=6.7 Hz), 1.15-1.46(m, 11H), 1.56(m, 1H), 1.67(m, 1H), 4.28(m, 1H),7.03(d, 1H, J=9.2 Hz), 7.17(dd, 1H, J=2.9 Hz, J=9.2 Hz), 7.47(d, 1H,J=2.9 Hz), 10.27(s, 1H); ¹³ C NMR (300 MHz, CDCl₃): δ13.97, 19.34,22.50, 25.32, 29.14, 31.69, 36.16, 75.32, 108.53, 120.72, 128.71,133.11, 149.78, 151.16; IR (CHCl₃): 3250(broad), 3010, 2930, 2840, 1600,1570, 1480, 1425, 1375, 1325, 1250, 1125, 1075, 975, 825 cm⁻¹ ; Massspectrum, m/z (rel.intensity): 267 (M⁺ 5), 155(100), 71(21), 57(21),55(10), 43(27);

Anal. Calcd. for C₁₄ H₂₁ NO₄ : C 62.90, H 7.92, N 5.24. Found: C 62.16,H 7.82, N 5.06.

Example 4 Synthesis of (S)-4'-(1-methyl-heptyloxy)-4-hydroxy-3-nitro-biphenyl (Compound 41, SchemeVIII, R₂ =(S) --OCH (CH₃) C₆ H₁₃)(S)-4'-(1-Methylheptyloxy)-4-biphenylyl benzoate

To an argon-flushed flask containing 2.32 g (8 mmol) of4'-hydroxy-4-biphenylyl benzoate and 1.25 eq of triphenylphosphine in200 ml of dry THF was added a solution of 1.052 g (8.08 mmol) of(R)-2-octanol dissolved in 15 ml of dry THF via syringe. Then 1.2 eq ofdiethyl azodicarboxylate in 30 ml of dry THF was added dropwise over 30min. The reaction mixture was stirred at room temperature for 20 h andthen 5 drops of water was added and stirring was continued for anadditional 1 h. The solvent was evaporated and the crude product wastriturated for 1 h in a mixture of hexanes/ethyl acetate [70/30]. Thesolution was filtered through a short silica gel pad and the solventevaporated. Flash chromatography on silica gel using hexanes/ethylacetate [98/2] as eluent afforded 2.42 g (75%) of(S)-4'-(1-methylheptyloxy)-4-biphenylyl benzoate (Compound 39, SchemeVIII, R₂ =(S) --OCH(CH₃)C₆ H₁₃) as a white solid (mp. 84° C.); R_(f)[hexanes/ethyl acetate 95/5]: 0.34; ¹ H NMR (300 MHz, CDCl₃): δ0.89 (t,3H, J=6.8 Hz), 1.14-1.68(m, 9H), 1.32(d, 3H, J=6.1 Hz), 1.75 (m, 1H),4.39 (m, 1H), 6.95(d, 2H, J=9 Hz), 7.25(d,2H, J=8.4 Hz), 7.46-7.68(m,7H), 8.22 (dd, 2H, J=1.2 Hz J=6.9 Hz); ¹³ C NMR (300 MHz, CDCl₃):δ14.02, 19.73, 22.55, 25.50, 29.24, 31.75, 36.48, 73.96, 116.10, 121.88, 127.72, 128.58, 129.61, 130.21, 132.64, 133.59, 138.79, 149.87,157.94, 165.30; IR (CHCl₃): 3020, 2930, 2850, 1745, 1600, 1500, 1260,1240, 1170, 1190, 1070, 1000, 840, 820 cm⁻¹ ; Mass spectrum, m/z (rel.intensity): 402(M⁺ 16), 290(14), 105(100), 77 (16), 43 (6) .

(S)-4'-(1-methylheptyloxy)-4-hydroxybiphenyl

The same procedure as that used for saponification of(S)-4-(1-methylheptyloxy)-3-nitro-phenol was used except the reactionwas carried out in a methanol/dichloromethane [4:1]mixture at 60° C.Flash chromatography with hexanes/ethyl acetate [93/7] afforded(S)-4'-(1-methylheptyloxy)-4-hydroxybiphenyl (Compound 40, Scheme VIII,R₂ =(S)--OCH(CH₃)C₆ H₁₃) as a white solid (mp 100.5° C.); R_(f)[hexanes/ethyl acetate 90/10]: 0.2; ¹ H NMR (300 MHz, CDCl₃): δ0.88(t,3H, J=6.6 Hz), 1.20-1.64(m, 9H), 1.33(d, 3H, J=6.1 Hz), 1.74(m, 1H),4.38(m, 1H), 5.07(s, 1H), 6.87(d,2H, J=8.5 Hz), 6.93(d, 2H, J=8.5 Hz),7.42(d, 2H, J =8.5 Hz), 7.44(d, 2H, J=8.5 Hz); ¹³ C NMR (300 MHz,CDCl₃): δ14.02, 19.73, 22.54, 25.51, 29.22, 31.74, 36.45, 74.17, 115.59,116.16, 127.74, 127.94, 133.22, 133.77, 154.55, 157.31; IR (CHCl₃):3560, 3350(broad), 3020, 2920, 2840, 1610, 1500, 1250, 1220, 1175, 825cm⁻¹. Mass spectrum, m/z(rel.intensity): 298(M⁺ 11), 186(100), 185(4),157(4).

Anal. Calcd. for C₂₀ H₂₆ O₂ : C 80.50, H 8.78. Found: C 80.41, H 8.77.

(S)-4'-(1-methylheptyloxy)-4-hydroxy-3-nitro-biphenyl

To an argon-flushed flask containing 0.127 g (1.5 mmol) of NaNO₃, 6.5 mg(0.015 mmol) of La(NO₃)₃.6 H₂ O, 1.2 ml of HCl and 1.5 ml of water wasadded a solution of 0.447 g (1.5 mmol) of(S)-4'-(1-methylheptyloxy)-4-hydroxy-biphenyl in 10 ml of ethyl ether.The reaction mixture was vigorously stirred at room temperature for 2hand 30min. Then water was added and the orange organic layer wasremoved. The aqueous layer was extracted several times with ethylacetate and the combined organic layers were washed with water until thewashes were pH˜6, and then with brine. The organic solution was driedand the solvent evaporated. The crude product was purified by flashchromatography using hexanes/ethyl acetate [97/3] as eluent, affording0.412 g (80%) of (S)-4'-(1-methylheptyloxy)-4-hydroxy-3-nitro-biphenyl(Compound 41, Scheme VIII, R₂ =(S)--OCH(CH₃)C₆ H₁₃) as a yellow solid(mp. 40° C.); R_(f) [hexanes/ethyl acetate [95/5]: 0.5; ¹ H NMR (300MHz, CDCl₃): δ0.88(t, 3H, J=6.6 Hz), 1.17-1.69 (m, 9H), 1.32 (d, 3H,J=6.1 Hz), 1.77(m, 1H), 4.39(m, 1H), 6.95(d, 2H, J=8.4 Hz), 7.20(d, 1H,J=8.7 Hz), 7.47(d, 2H J=8.4 Hz), 7.78(dd, 1H J=2.4 Hz, J=8.7 Hz),8.25(d, 1H, J=2.4 Hz), 10.55(s, 1H); ¹³ C NMR (300 MHz, CDCl₃): δ14.00,19.65, 22.53, 25.45, 29.21, 31.74, 36.40, 74.03, 116.29, 120.25, 122.03,127.77, 130.35, 133.68, 133.75, 135.92, 153.86, 158.37; IR (CHCl₃):3240(broad), 3020, 2950, 2850, 1625, 1600, 1510, 1485, 1425, 1325, 1240,1225, 1175, 825 cm⁻¹ ; Mass spectrum, m/z (rel. intensity): 343 (M⁺ 6),231 (100), 230(1), 214(2), 201(5), 185(5), 57(10), 34(15).

Anal. Calcd. for C₂₀ H₂₅ NO₄ : C 69.95, H 7.34, N 4.08. Found: C 70.24,H 7.44, N 4.07.

Example 5 Synthesis of (S)-4-(1-methylheptyloxy)-3-nitro-benzoylchloride (Compound 25, Scheme IV, R₁ =(S) --OCH(CH₃)C₆ H₁₃)(S)-Methyl-4-(1-methyheptyloxy)-3-nitrobenzoate

Methyl 4-hydroxy-3-nitrobenzoate was coupled with (R)-2-octanol usingthe same procedure as that given for alkylation of phenol 9, Scheme I,to give (S)-methyl-4-(1-methyheptyloxy)-3-nitrobenzoate (Compound 23,Scheme IV, R₁ =(S)--OCH(CH₃)C₆ H₁₃). The product was purified by flashchromatography with hexanes/ethyl acetate (95/5) as eluent affording ayellow liquid, R_(f) [hexanes/ethyl acetate 95/5]: 0.25; ¹ H-NMR (300MHz, CDCl₃): δ0.82 (t, 3H, J =7.1 Hz); 1.14-1.50 (m, 8H); 1.34(d, 3H,J=6.1 Hz); 1.60(m, 1H); 1.75(m, 1H); 3.87(s, 3H); 4.57(m, 1H); 7.06(d,1H, J=8.9 Hz); 8.11(dd, 1H, J=2.2 Hz, J =8.9 Hz); 8.39(d, 1H, J=2.2 Hz);¹³ C-NMR (300 MHz, CDCl₃): δ13.96, 19.31, 22.47, 25.06, 29.02, 31.60,36.00, 52.35, 76.80, 114.63, 121.80, 127.17. 134.80, 140.27, 154.91,165.08; Mass Spectrum , m/z(rel.intensity): 309 (M⁺ 1), 197 (32),166(46),112(48), 71(63), 57(100), 55(46).

Anal. Calcd. for C₁₆ H₂₃ NO₅ : C 62.12, H 7.49, N 4.53. Found: C 62.11,H 7.36, N 4.86.

(S)-4-(1-Methyl-heptyloxy)-3-nitro-benzoic acid

The same procedure as that used for saponification of(S)-4-(1-methylheptyloxy)-3-nitro-phenol was used, affording(S)-4-(1-methyl-heptyloxy)-3-nitro-benzoic acid (Compound 24, Scheme IV,R₁ =(S)--OCH(CH₃)C₆ H₁₃) as a white solid after recrystallization fromhexanes; R_(f) [hexanes/ethyl acetate 1:1+a drop of acetic acid]: 0.28;¹ H NMR (300 MHz, CDCl₃): δ0.83(t, 3H, J=6.8 Hz), 1.14-1.50(m,8H),1.37(d, 3H, J=6.1 Hz), 1.64(m, 1H), 1.79(m, 1H), 4.63(m, 1H), 7.10(d,1H, J =8.9 Hz), 8.20(dd, 1H, J=2.2 Hz, J=8.9 Hz), 8.48(d, 1H, J=2.2 Hz);¹³ C NMR (300 MHz, CDCl₃): δ13.91, 19.34, 22.47, 25.07, 29.04, 31.62,36.04, 77.15, 114.81, 120.89, 127.87, 135.35, 140.61, 155.71, 170.20; IR(CHCl₃): 3400-2500, 2940, 2850, 1680, 1610, 1530, 1400, 1350, 1280,1125, 1075, 925 cm⁻¹ ; Mass spectrum, m/z(rel.intensity): 295(M⁺ 17),184(100), 112(47, 71(53), 57(70), 55(35), 43(80), 41(79).

(S)-4-(1-methylheptloxy)-3-nitro-benzol chloride

Acid 24 (Scheme IV, R₁ =(S)--OCH(CH₃)C₆ H₁₃) was converted to the acidchloride using oxalyl chloride in benzene. After removal of solvent, thecrude acid chloride 25 (Scheme IV, R₁ =(S)--OCH(CH₃)C₆ H₁₃) was useddirectly in the coupling reactions without further purification orcharacterization.

Example 6 Synthesis of (S)-4'-(1-methylheptyloxy)-3'-nitro-4-biphenylcarboxylic acid chloride (Compound 32, Scheme V, R₁ =(S)--OCH(CH₃)C₆ H₁₃) Methyl 4'-hydroxy-3'-nitro-4-biphenylcarboxylate

To an argon-flushed flask charged with 0,544 g (6.4 mmol) of NaNO₃, 27.7mg (0,064 mmol) of La(NO₃)₃.6 H₂ O, 9 ml of water and 5.1 ml of HCl, wasadded a solution of 1.46 g (6.4 mmol) of methyl4'-hydroxy-biphenylcarboxylate (28, Scheme V, Literature: Otterholm, B.,(1987), Ph.D. Thesis, Chalmers Technical University, Goteborg, Sweden)dissolved in 25 ml of THF/ethyl ether (55:45). The reaction mixture wasvigorously stirred at 55° C. for 7 h. After cooling, water was added andthe organic layer removed. The aqueous layer was extracted several timeswith ethyl ether and the combined organic layers were washed with wateruntil the washes were pH˜6. The organic solution was dried and thesolvent evaporated. Flash chromatography on silica gel withhexanes/ethyl acetate [90/10] as eluent afforded 1.5 g (85%) of methyl4'-hydroxy-3'-nitro-4-biphenylcarboxylate (Compound 29, Scheme V, R₁=(S)--OCH(CH₃)C₆ H₁₃) as a yellow solid. Recrystallization fromcyclohexane gave material with mp. 143° C.; R_(f) [hexanes/ethyl acetate90/10]: 0.26; ¹ H NMR (300 MHz, CDCl₃): δ3.92(s, 3H), 7.24(d, 1H, J=8.8Hz), 7.59(d, 2H, J=8.5 Hz), 7.84(dd, 1H, J=2.2 Hz, J=8.8 Hz), 8.09(d,2H, J=8.5 Hz), 8.20(d, 1H, J=2.2 Hz), 10.60(s, 1H); ¹³ C NMR (300 MHz,CDCl₃): δ52.19, 120.71, 123.77, 126.57, 129.58, 130.40, 132.55, 133.82,136.18, 142.46, 154.90, 166.66; IR (CHCl₃): 3240 (broad), 1040, 2950,1720, 1625, 1600, 1540, 1490, 1425, 1320, 1290, 1210, 1190, 980, 825cm⁻¹ ; Mass spectrum, m/z (rel. intensity): 273 (M⁺ 85), 242 (100), 196(11), 168(14), 139.(41), 59(9).

Anal. Calcd. for C₁₄ H₁₁ NO₅ : C 61.54, H 4.06, N 5.13. Found: C 62.10,H 4.00, N 4.92.

(S)-Methyl 4'-(1-methylheptyloxy)-3'-nitro-4-biphenylcarboxylate

Methyl 4'-hydroxy-3'-nitro-4-biphenylcarboxylate was coupled with(R)-2-octanol using the same procedure as that given for alkylation ofphenol 9, Scheme I, to give (S)-methyl4'-(1-methylheptyloxy)-3'-nitro-4-biphenylcarboxylate (Compound 30,Scheme V, R₁ =(S)--OCH(CH₃)C₆ H₁₃) as a slightly yellow solid afterflash chromatography with hexanes/ethyl acetate [93/7].Recrystallization from hexanes gave material with mp 69° C.; R_(f)[hexanes/ethyl acetate 90/10]: 0.23; ¹ H-NMR (300 MHz, CDCl₃): δ 0.85(t,3H, J=6.8 Mz), 1.20-1.52(m, 8H), 1.36(d, 3H, J=6.1 Hz), 1.62(m, 1H),1.80(m, 1H), 3.92(s, 3H), 4.53(m, 1H), 7.12(d, 1H, J=8.7 Hz), 7.59(d,2H, J=8.4 Hz), 7.72(dd, 1H, J=2.4 Hz, J=8.7 Hz), 8.02(d, 1H, J=2.4 Hz),8.08(d, 2H, J=8.4 Hz); ¹³ C NMR (300 Mz, CDCl₃): δ 13.99, 19.46, 22.50,25.19, 29.09, 31.65, 36.13, 52.17, 76.58, 116.07, 124.04, 126.53,129.31, 130.35, 131.90, 132.06, 141.11, 142.81, 151.49, 166.75; IR(CHCl₃): 3020, 2920, 2850, 1725, 1625, 1620, 1540, 1490, 1360, 1280,1180, 1120, 1020, 820 cm⁻¹ ; Mass spectrum m/z(rel.intensity): 385(M⁺47), 354(27), 273(100), 242(34), 139(17), 71(10) 57(20), 43(45), 41(38).

Anal. Calcd. for C₂₂ H₂₇ NO₅ : C 68.55, H 7.06, N 3.63. Found: C 68.65,H 7.06, N 3.59.

S-4'(1-methyl-heptyloxy)-3'-nitro-4-biphenylcarboxylic acid

The same procedure as that used for saponification of(S)-4-(1-methylheptyloxy)-3-nitro-phenol was used except that thereaction was carried out at 60° C., affording(S)-4'-(1-methyl-heptyloxy)-3'-nitro-4-biphenylcarboxylic acid (Compound31, Scheme V, R₁ =(S)-OCH(CH₃)C₆ H₁₃) as a yellow solid; R_(f)[hexanes/ethyl acetate 50% +a drop of acetic acid]: 0.36; ¹ H NMR (300MHz, CDCl₃): δ 0.86(t, 3H, J=6.7 Hz), 1.20-1.55(m, 8H), 1.37(d, 3H,J=6.1 Hz), 1.65(m, 1H), 1.80(m, 1H), 4.55(m, 1H), 7.14(d, 1H, J=8.7 Hz),7.64(d, 2H, J=8.4 Hz), 7.74(dd, 1H, J=2.4 Hz, J=8.7 Hz), 8.05(d, 1H,J=2.4 Hz), 8.17(d, 2H, J=8.4 Hz); ¹³ C NMR (300 MHz, CDCl₃): δ 13.99,19.47, 22.51, 25.17, 29.11, 31.64, 36.15, 76.65, 116.13 124.13, 128.42,131.04, 132.12, 141.16, 143.78, 151.66, 171.93; Mass spectrum,m/z(rel.intensity): 371(M⁺ 0.38), 259(100), 139(11) 71(7), 57(16),55(11), 43(27), 41(23).

(S)-4'-(1-methyl-heptyloxy)-3'-nitro-4-biphenylcarboxylic acid chloride

Acid 31 (Scheme V, R₁ =(S)-OCH(CH₃)C₆ H₁₃) was converted to the acidchloride using oxalyl chloride in benzene. After removal of solvent, thecrude acid chloride 32 (Scheme V, R₁ =(S)--OCH(CH₃)C₆ H₁₃) was useddirectly in the coupling reactions without further purification orcharacterization.

Example 7 Synthesis of (S)-4-(1-methylheptyloxy)-2-nitro-benzoylchloride (Compound 38, Scheme VI, R₁ =(S)--OCH(CH₃)C₆ H₁₃)(S)-4-(1-Methylheptyloxy)-2-nitro-toluene

4-Methyl-3-nitrophenol (Compound 33, Scheme VI) was coupled with(R)-2-octanol using the same procedure as that given for alkylation ofphenol 9, Scheme I, to give (S)-4-(1-methylheptyloxy)-2-nitro- toluene(Compound 34, Scheme VI, R_(l) =(S)--OCH(CH₃)C₆ H₁₃) as a yellow liquid;R_(f) [Hexanes/ethyl acetate 99/1]: 0.26; ¹ H NMR (300 MHz, CDCl₃):δ0.87(t, 3H, J=6.6 Hz), 1.16-1.65(m, 12H), 1.70(m, 1H), 2.50(s, 3H),4.37(m, 1H), 7.02(dd, 1H ,J=2.7 Hz, J=8.5 Hz), 7.19(d, 1H, J=8.5 Hz),7.47(d, 1H, J=2.7 Hz); ¹³ C NMR (300 MHz, CDCl₃): δ13.97, 19.41, 19.63,22.51, 25.32, 29.14, 31.69, 36.20, 74.72, 111.05, 121.44, 125.12,133.44, 149.5, 156.77; IR (CHCl₃): 3020, 2940, 2850, 1620, 1550, 1525,1490, 1375, 1300, 1240, 1220, 1110, 1050, 975, 860, 825 cm⁻¹ ; Massspectrum, m/z(rel.intensity): 265(M⁺ 11), 153(33), 136(100), 112(21),71(40), 57(70), 51(11), 43(78), 41(66).

Anal. Calcd. for C₁₅ H₂₃ NO₃ : C 67.90, H 8.74, 5.28. Found: C 67.42, H8.49, N 5.51.

(S)-α-Bromo-4-(1-methylheptyloxy)-2-nitrotoluene

A suspension of 6.1 g (34.4 mmol) of NBS and 4 g of silica gel in 125 mlof dry dichloromethane was stirred under argon for 30 min. Then asolution of 4.56 g (17.2 mmol) of(S)-4-(1-methylheptyloxy)-2-nitro-toluene in 150 ml of dichloromethanewas added via syringe. The reaction mixture was stirred at roomtemperature for 72 h. The resulting suspension was filtered through ashort silica gel pad and the pad was washed several times withdichloromethane. The solvent was evaporated and the crude productextracted with a mixture of hexanes/ethyl acetate [95/5]. The suspensionwas filtered, the solvent removed and the residue was purified by flashchromatography using hexanes as eluent, affording 4.6 g (78%) of(S)-α-Bromo-4-(1-methylheptyloxy)-2-nitrotoluene (Compound 35, SchemeVI, R₁ =(S)--OCH(CH₃)C₆ H₁₃) as a yellow liquid; R_(f) [hexanes/ethylacetate 98/2]: 0.26; ¹ H NMR (300 MHz, CDCl₃): δ0.86(t, 3H, J =6.7 Hz),1.18-1.48(m, 8H), 1.30(d, 3H, J=6.1 Hz), 1.58(m 1H), 1.70(m, 1H),4.40(m, 1H), 4.77(s, 2H), 7.06(dd, 1H, J=2.7 Hz, J=8.5 Hz), 7.40(d, 1H,J=8.5 Hz), 7.50(d, 1H, J=2.7 Hz); ¹³ C NMR (300 MHz, CDCl₃): δ13.98,19.36, 22.50, 25.28, 29.10, 29.25, 31.67, 36.12, 75.00, 111.93, 121.08,124.14, 133.61, 148.69, 158.92; IR (CHCl₃): 3020, 2930, 2850, 1625,1525, 1500, 1350, 1320, 1250, 1100, 975, 850, 825 cm⁻¹ ; Mass spectrum,m/z(rel.intensity): 345(M⁺ +1.38), 43(M⁺ -1 1.35), 264(37), 152(100),112(28), 71(59), 57(93), 55(38), 43(93), 41(70).

Anal. Calcd. for C₁₅ H₂₂ BrNO₃ : C 52.34, H 6.44, Br 23.21, N 4.07.Found: C 52.38, H 6.33, N 4.37, Br 23.10.

(S)-[4-(1-methylheptyloxy)-2-nitro-phenyl]-methyl nitrate

To a solution of 3.95 g (11.5mmol) of(S)-α-bromo-4-(1-methyl-heptyloxy)-2-nitro-toluene in 160 ml of dioxanewas added a solution of 8.03 g (47.26 mmol) of AgNO₃ in 16 ml of water.The reaction mixture was stirred at room temperature for 18 h. Theprecipitate was filtered and washed with ethyl acetate. The filtrate wastreated with 150 ml of water and the organic layer separated. Theaqueous layer was extracted with ethyl acetate and the combined organiclayers evaporated. The resulting crude product was purified by flashchromatography with hexanes/ethyl acetate [100/0.2] and used in the nextstep without further purification (2.14 g of a yellow liquid, 57%yield); ¹ H NMR (300 MHz, CDCl₃): δ0.86(t, 3H, J=6.8 Hz), 1.18-1.50(m,8H), 1.31(d, 3H, J=6.1 Hz), 1.60(m,1H), 1.72(m, 1H), 4.42(m, 1H),5.76(s, 2H), 7.13(dd, 1H, J=2.5 Hz J=8.6 Hz), 7.43(d, 1H, J =8.6 Hz),7.61(d, 1H, J=2.5 Hz); IR (CHCl₃): 3020, 2940, 2840, 1640, 1530, 1500,1460, 1115, 975, 900, 850, 825 cm⁻¹ ; Mass spectrum, m/z(rel.intensity):326(M⁺ 2), 264(2), 151(13), 112(34), 71(70), 57(100), 55(28), 43(79),41(47).

(S)-4-(1-methyl-heptyloxy)-2-nitro-benzaldehyde

To a solution of 1.96 g (6 mmol) of the methyl-nitrate prepared above in96 ml of dioxane was added a solution of KOH (5.52 g) in 20 ml of water.The reaction mixture was stirred at room temperature under argon for 20h. Then the mixture was poured into 120 ml of water and the resultingsolution was treated with brine (48 ml ). This mixture was thenextracted with dichloromethane, the extract dried with MgSO₄, andsolvent evaporated. Flash chromatography of-the resulting crude productusing hexanes/ethyl acetate [100/0.4] furnished(S)-4-(1-methylheptyloxy)-2-nitrobenzaldehyde (95%) (Compound 36, SchemeVI, R₁ =(S) --OCH (CH₃) C₆ H₁₃) as a yellow liquid; R_(f) [hexanes/ethylacetate 98/2]: 0.2; ¹ H NMR (300 MHz, CDCl₃): δ0.85(t, 3H, J=6.6 Hz),1.16-1.51(m, 8H), 1.34(d, 3H, J=6.1 Hz), 1.60(m, 1H), 1.76(m, 1H),4.50(m, 1H), 7.15.(dd, 1H, J=2.4 Hz, J =8.8 Hz), 7.43(d, 1H, J=2.4 Hz),7.93(d, 1H, J=8.8 Hz), 10.24(s, 1H); ¹³ C NMR (300 MHz, CDCl₃): δ13.95,19.29, 22.47, 25.21, 29.05, 31.63, 36.05, 75.63, 110.81, 120.02, 122.86,131.50, 151.84, 162.71, 186.98; Mass spectrum, m/z(rel.intensity):279(M⁺ 1), 167(31), 120(11), 112(14), 92(9), 71(70), 57(100), 43(85),41(57).

Anal. Calcd. for C₁₅ H₂₁ NO₄ : C 64.50, H 7.58, N 5.01. Found: C 64.11,H 7.46, N 5.25.

(S)-4-(1-Methylheptyloxy)-2-nitrobenzoic acid

To a solution of 1.086 g (3.89 mmol) of(S)-4-(1-methylheptyloxy)-2-nitrobenzaldehyde in 40 ml of acetone wasadded a solution of KMnO₄ (0.984 g, 6.23 mmol) in 47 ml of waterdropwise. The reaction mixture was stirred at room temperature for 6 hand then treated with 5% Na₂ SO₃ (100 ml), acidified with conc. HCl (pH:4-5), and the resulting solution was extracted with ethyl ether severaltimes. The organic extract was concentrated and extracted with 10% NaOHsolution. The alkaline extract was washed with ether, acidified withconc. HCl/ice, and the resulting solution extracted with ethyl ether.The organic layer was washed with water, dried, and the solventevaporated. (S)-4-(1-Methylheptyloxy)-2-nitrobenzoic acid (Compound 37,Scheme VI, R₁ =(S)--OCH(CH₃)C₆ H₁₃) was obtained as a dark orange liquid(0.8 g, 70%) which was used in the next step without furtherpurification; R_(f) [hexanes/ethyl acetate 70/30+1 drop of acetic acid]:0.16; ¹ H NMR (300 MHz, CDCl₃): δ0.86(t, 3H, J=6.8 Hz), 1.16-1.48(m,8H), 1.32(d, 3H, J-=5.(Hz), 1.60(m, 1H), 1.72(m, 1H), 4.45(m, 1H),7.02(dd, 1H, J=2.4 Hz J=8.8 Hz), 7.09(d, 1H, J=2.4 Hz), 7.90(d, 1H,J=8.8 Hz); ¹³ C NMR (300 MHz, CDCl₃): δ13.98, 19.22, 22.51, 25.24,29.14, 31.68, 36.14, 79.94, 110.26, 117.84, 118.98, 132.97, 150.69,160.61, 170.81; Mass spectrum, m/z(rel.intensity): 295(M⁺ 1), 265(9),166(8), 135(36), 112(14), 71(66), 57(100), 55(27), 43(94), 41(69).

(S)-4-(1-Methylheptyloxy)-2-nitrobenzoyl chloride

Acid 36 (Scheme VI, R₁ =(S)--OCH(CH₃)C₆ H₁₃) was converted to the acidchloride using oxalyl chloride in benzene. After removal of solvent, thecrude acid chloride 37 (Scheme VI, R₁ =(S)--OCH(CH₃)C₆ H₁₃) was useddirectly in the coupling reactions without further purification orcharacterization.

Example 8 General procedure for coupling phenols with acid chlorides,and synthesis of exemplary compounds of formula I Procedure for couplingphenols with acid chloride

To a flame dried and argon-flushed flask containing a suspension of 2.1mmol of NaH in 30 ml of dry THF was added a solution of 2.1 mmol ofphenol in 17 ml of dry THF via syringe. After stirring for 20-45 min, asolution of 2.1 mmol of acid chloride in 12 ml of dry THF was added. Thereaction mixture was then allowed to stir at room temperature. When thereaction was judged complete by TLC (19-22 h), the reaction was quenchedby addition of water, and the resulting aqueous phase was extracted withethyl ether. The combined organic extracts were washed with 10% aqueousHCl, 5% aqueous NaOH and brine, then dried and filtered. Once thefiltrate was evaporated to dryness, the crude product was purified byflash chromatography to give the product ester in 70-92% yield. In orderto obtain material suitable for liquid crystals studies, several flashchromatographic purifications and often recrystallizations from hexaneswere required to obtain material of sufficient purity as judged by TLCand the sharpness of the LC phase transitions or melting points

Analytical data for compounds of formula I(S)-4"-(1-Methylheptyloxy)-3"-nitrophenyl-4'-n-decyloxy-4-biphenylcarboxylate

The compound of formula I where R₁ =n--C₁₀ H₂₁ O, R₂ =(S)--OCH(CH₃)C₆H₁₃, m=0, n=1, k=1, X₁ =NO₂, and X₂ -X₄ =H (Scheme I) was purified byflash chromatography with toluene/hexanes [80/20]; R_(f) [hexanes/ethylacetate 95/5]: 0.22; [α]_(D) ²⁵ : +12.3°(2.74, CHCl₃); ¹ H NMR (300 MHz,CDCl₃): δ0.87(m, 6H), 1.18-1.54(m, 22H), 1.35(d, 3H, J=6.1 Hz), 1.62(m,1H), 1.80(m, 3H), 4.00(t, 2H, J=6.6 Hz), 4.48(m, 1H), 6.99(d, 2H, J=8.7Hz), 7.09(d, 1H, J=9.3 Hz), 7.38(dd, 1H, J=2.8 Hz, J=9.3 Hz), 7.56(d,2H, J=8.3 Hz), 7.68(d, 2H, J=8.3 Hz), 7.71(d, 1H, J=2.8 Hz), 8.19(d, 2H,J =8.7 Hz); ¹³ C NMR (300 MHz, CDCl₃ : δ13.99, 14.04, 19.47, 22.51,22.62, 25.18, 25.99, 29.11, 29.19, 29.26, 29.34, 29.50, 29.52, 31.67,31.84, 36.19, 68.15, 77.00, 115.04, 116.51, 119.14, 126.68, 127.26,128.40, 130.79, 131.78, 140.55, 142.95, 146.43, 149.53, 159.75, 164.92;IR (CHCl₃): 3020, 2940, 2860, 1740, 1610, 1540, 1490, 1300, 1260, 1170,1015, 825 cm⁻¹ ; Mass spectrum, m/z(rel.intensity): 603(M⁺ 0.03),337(100), 197 (13), 57(5), 55(3), 43(12).

Anal. Calcd. for C₃ H₄₉ NO₆ : C 73.60, H 8.18, N 2.32. Found: C 73.98, H8.23, N 2.29.

S -4"-(1-Methylheptloxy)-3"-nitro-4'-biphenylyl-4-n-decyloxy-benzoate

The compound of formula I where R₁ =n--C₁₀ H₂₁ O, R₂ =(S)--OCH(CH₃)C₆H₁₃, m=1, n=0, k=1, X₁ =NO₂, and X₂ -X₄ =H (Scheme II) was purified byflash chromatography with hexanes/ethyl acetate [99/1]; R_(f)[hexanes/ethyl acetate 95/5]: 0.16. [α]_(D) ²⁵ : +7.2° (c 2.57, CHCl₃);¹ H NMR (300 MHz, CDCl₃): δ0.88(t, 6H, J=6.6 Hz), 1.15-1.50(m, 22H),1.36(d, 3H, J=6.1 Hz), 1.62(m, 1H), 1.80(m, 3H), 4.03(t, 2H, J =6.4 Hz),4.52(m, 1H), 6.96(d, 2H, J=8.7 Hz), 7.11(d, 1H, J =8.7 Hz), 7.26(d, 2H,J=8.7 Hz), 7.56(d, 2H, J=8.4 Hz), 7.67(dd, 1H, J=2.1 Hz, J=8.7 Hz),7.98(d, 1H, J=2.1 Hz), 8.13(d, 2H, J=8.4 Hz); ¹³ C NMR (300 MHz, CDCl₃):δ14.00, 14.07, 19.51, 22.52, 22.63, 25.20, 25.92, 29.04, 29.13, 29.26,29.31, 29.50, 31.68, 31.85, 36.20, 68.33, 76.58, 114.35, 116.14, 121.34,122.47, 123.78, 127.78, 131.94, 132.35, 132.63, 136.16, 141.15, 150.89,163.70, 164.9.5; IR (CHCl₃): 3020, 2940, 2850, 1740, 1600, 1540, 1490,1350, 1270, 1210, 1175, 1075, 1025, 975, 840 cm⁻¹ ; Mass spectrum,m/z(rel.intensity): 603(M⁺ 0.03), 261(100), 121(66), 57(10), 55(6),43(17).

Anal. Calcd. for C₃₇ H₄₉ NO₆ : C73.60, H 8.18, N 2.32. Found: C 73.68, H8.32, N 2.33.

(S)-4"-(1-Methylheptyloxy)-2"-nitrophenyl-4'-n-decyloxy-4-biphenylcarboxylate

The compound of formula I where R₁ =n--C₁₀ H₂₁ O, R₂ =(S)-OCH(CH₃)C₆H₁₃, m=0, n=1, k=1, X₂ =NO₂, and X₁, X₃ and X₄ =H Scheme III) waspurified by flash chromatography with hexanes/dichloromethane [77/23];R_(f) [hexanes/ethyl acetate 90/10]: 0.57. [α]_(D) ²⁵ :+3.8° (c 3.16,CHCl₃); ¹ H NMR (300 MHz, CDCl₃): δ0.88(m, 6H), 1.18-1.54(m, 22H),1.34(d, 3H, J=6.1 Hz), 1.62(m, 1H), 1.80 (m, 3H), 4.03(t, 2H, J=6.6 Hz),4.40(m, 1H), 7.00(d, 2H, J=8.7 Hz), 7.18(dd, 1H, J=2.7 Hz J=9 Hz),7.26(d, 1H, J=9 Hz), 7.59(d, 2H, J=9 Hz), 7.61(d, 1H, J =2.7 Hz),7.70(d, 2H, J=8.7 Hz); 8.22(d, 2H, J=¹³ C NMR (300 MHz, CDCl₃): δ 14.00,14.05, 19.39, 22.52, 22.63, 25.34, 25.99, 29.15, 29.20, 29.28, 29.35,29.52, 29.53, 31.71, 31.85, 36.19, 68.13, 75.28, 11.67, 115.00, 122.38,126.06, 126.58, 126.68, 128.44, 131.04, 131.93, 137.39, 142.10, 146.45,156.10, 159.69, 164.82; IR (CHCl₃): 3020, 2930, 2850, 1740, 1620, 1540,1510, 13.40, 1270, 1250, 1170, 1140, 1075, 975, 825 cm⁻¹ ; Massspectrum, m/z (rel. intensity): 603(M⁺ 0.5), 337(100), 214(27), 197(18),169(71), 155(22), 150(28), 119(11), 71(13), 69(41), 57(31), 55(18),43(42).

(S)-[4"-n-Decyloxy-4'-biphenylyl]-4-(1-methylheptyloxy)-3-nitrobenzoate

The compound of formula I where R₂ =n--C₁₀ H₂₁ O, R₁ 32 (S)--OCH(CH₃)C₆H₁₃, m=1, n=0, k=1, X₂ =NO₂, and X₁, X₃ and X₄ =H (Scheme IV) waspurified by flash chromatography with toluene/hexanes [88/12]; R_(f)[toluene/hexanes 90/10]: 0.45. [α]_(D) ²⁵ :+5.8° (c 2.26, CHCl₃); ¹ HNMR (300 MHz, CDCl₃): δ 0.88(t, 6H, J=6.8 Hz), 1.15-155 (m, 22H),1.33(d, 3H, J=6.1 Hz), 1.67(m, 1H), 1.82(m, 1H), 3.99(t, 2H, J=6.4 Hz),4.65(m, 1H), 6.97(d, 2H, J=8.8 Hz), 7.16(d, 1H, J=9 Hz), 7.24(d, 2H,J=8.8 Hz), 7.51(d, 2H J=8.5 Hz), 7.59(d, 2H, J=8.5 Hz), 8.32(dd, 1H,J=2.2 Hz J=9 Hz), 8.63(d, 1H, J=2.2 Hz); ¹³ C NMR (300 MHz, CDCl₃): δ14.00, 14.07, 19.34, 22.05, 22.09, 25.09, 26.01, 29.05, 29.24, 29.28,29.36, 29.51, 29.56, 31.64, 31.85, 36.00, 68.09, 77.00, 114.83 , 121.13, 121.74, 127.76, 127.80, 128.12, 132.57, 135.42, 139.03, 140.44,149.52, 155.43, 158.89, 163.34; IR (CHCl₃): 3010, 2940, 2840, 1740,1610, 1525, 1490, 1310, 1280, 1240, 1200, 1170, 1090, 1000, 840, 825cm⁻¹ ; Mass spectrum, m/z(rel.intensity): 603(M⁺ 21), 326(28), 248(37),246(30), 186(87), 166(100), 136(70), 71(11), 57(26), 55(22), 43(43).

Anal. Calcd. for C₃₇ H₄₉ NO₆ : C 73.60, H 8.18, N 2.32. Found: C 73.97,H 8.12, N 2.34.

(S)-4"-n-Decyloxyphenyl-4'-(1-methylheptyloxy)-3'-nitro-4-biphenylcarboxylate

The compound of formula I where R₂ =n--C₁₀ H₂₁ O, R₁ =(S)--OCH(CH₃)C₆H₁₃, m=0, n=1, k=1, X₂ =NO₂, and X₁, X₃ and X₄ =H (Scheme IV) waspurified by flash chromatography with toluene/hexanes [75/25]; R_(f)[hexanes/ethyl acetate 90/10]: 0.41. [α]_(d) ²⁵ :+5.8° (c 2.46, CHCl₃);¹ H NMR (300 MHz, CDCl₃): δ 0.88(m, 6H), 1.16-1.54(m, 22H), 1.37(d, 3H,J=5.9Hz), 1.64(m, 1H), 180(m, 3H), 3.94(t, 2H, J=6.6 Hz), 4.55(m, 1H),6.92(d, 2H, J=9 Hz), 7.17(d, 2H, J=9 Hz), 7.14(d, 1H, J=8.8 Hz), 7.66(d,2H, J=8.4 Hz), 7.76(dd, 1H, J=2.4 Hz J=8.8 Hz), 8.06(d, 1H, J=2.4 Hz),8.24(d, 2H J=8.4 Hz); ¹³ C NMR (300 MHz, CDCl₃): δ 13.98, 14.04, 19.47,22.50, 22.62, 25.17, 25.99, 29.11, 29.22, 29.26, 29.51, 29.52, 31.66,31.84, 36.16, 68.43, 76.66, 115.14, 116.16, 122.35, 124.09, 126.68,128.87, 130.92, 131.82, 132.09, 141.23, 143.40, 144.23, 151.61, 157.02,165.21; IR (CHCl₃): 3040, 2940, 2860, 1735, 1610, 1510, 1530, 1360,1275, 1190, 1180, 1070, 1020, 825 cm⁻¹ ; Mass spectrum,m/z(rel.intensity): 603(M⁺ 0.6), 573(2), 354(44), 324(30), 242(100),212(46), 110(33), 57(19), 55(14), 43(34).

Anal. Calcd. for C₃₇ H₄₉ NO₆ : C 73.60, H 8.18, N 2.32. Found: C 73.60,H 8.34, N 2.35.

(S)-[4"-n-Decyloxy-4'- biphenylyl]-4-(1-methylheptyloxy)-2-nitrobenzoate

The compound of formula I where R₂ =n--C₁₀ H₂₁ O, R₁ =(S)--OCH(CH₃)C₆H₁₃, m=1, n=0, k=1, X₂ =NO₂, and X₁, X₃ and X₄ =H (Scheme IV) waspurified by flash chromatography with hexanes/dichloromethane [75/25];R_(f) [hexanes/ethyl acetate 95/5]: 0.19. [.sup.α ]_(D) ²⁵ :+2.1° (c2.72, CHCl₃ ]); ¹ H NMR (300 MHz, CDCl₃): δ0.87(m, 6H), 1.16-1.54(m,22), 1.34(d, 3H, J=6.1 Hz), 1.62(m, 1H), 1.72(m, 3H), 3.97(t, 2H, J=6.6Hz), 4.48(m, 1H), 6.94(d, 2H, J=8.5 Hz), 7.12(dd, 1H, J=2.4 Hz J=8.8Hz), 7.23(d, 2H, J=8.5 Hz), 7.29(d, 1H, J=2.4 Hz), 7.47(d, 2H, J=8.5Hz), 7.55(d, 2H, J=8.5 Hz), 7.90(d, 1H, J=8.8 Hz); ¹³ C NMR (300 MHz,CDCl₃): δ14.00 , 14.06, 19.32 , 22.52 , 22.63 , 25.26, 26.01, 29.09,29.24, 29.28, 29.36, 29.52, 29.54, 31.67, 31.85, 36.05, 68.10, 75.48,110.85, 114.84, 117.08, 118.74, 121.52, 127.80, 128.16, 132.51, 132.67,139.18, 149.47, 151.05, 158.89, 161.63 , 163.46; Mass spectrum,m/z(rel.intensity): 603 (M⁺ 0.3), 325(20), 201(64), 185(19), 166(8),91(100), 71(17), 57(37) 43(51), 41(54).

(S,S)-4,4'-Di-(1-methylheptyloxy)-3,3'-dinitrophenylbenzoate

The compound of formula I where R₂ =(S)-OCH(CH₃)C₆ H₁₃), R₁=(S)-OCH(CH₃)C₆ H₁₃, m=0, n=1, k=1, X₁ and X₂ : NO₂, X₃ and X₄ =H(Scheme VII ) was purified by flash chromatography with hexanes/ethylacetate [88/12]; R_(f) [Hexanes/ethyl acetate 90/10]: 0.24. [α]_(D) ²⁵ :+18.9° (c 2.75, CHCl₃); ¹ H NMR (300 MHz, CDCl₃): δH, J=6.8 Hz),1.20-1.55(m, 16H), 1.37 (d, 3H, J=6.1 Hz), 0.88(t, 6H, J=6.1 Hz),1.68(m, 2H), 1.82(m, 2H), 4.50(m, 1H), 1.41(d,7.11(d, 1H, J=9 Hz),7.17(d, 1H, J=9 Hz), 7.37(dd, 4.62(m, 2.7 Hz, J=9 Hz), 7.71(d, 1H, J=2.7Hz), 8.28(dd, 1H, J =2.1 Hz J=9 Hz), 8.58(d, 1H, J=2.1 Hz); ¹³ C NMR(300 MHz, ¹ H, J=CDCl₃): δ13.96, 19.28, 19.41, 22.45, 22.47, 25.03,25.14, 29.00, 29.07, 31.57, 31.69, 35.95, 36.13, 77.00, 77.10, 114.92,116.47, 119.00, 120.22, 127.05, 127.78, 135,44 , 140.38, 142.38, 149.72,155.72, 162.97; IR (CHCl₃): 3010, 2930, 2850, 1740, 1610, 1540, 1360,1290, 1200, 1110, 1075, 880, 825 cm⁻¹ ; Mass. spectrum,m/z(rel.intensity): 544(M* 0.7), 278(100), 166(100), 120(63), 112(18),71(79), 57(100), 55(54), 43(100), 41(81).

Anal. Calcd. for C₂₉ H₄₀ N₂ O₈ : C 63.95, H 7.40, N 5.14. Found: C63.53, H 7.52,, N 5.12.

(S,S)-4,4'-Di-(1-methylheptyloxy-3,3'-dinitro-4'-biphenylylbenzoate

The compound of formula I where R₂ =(S)-OCH(CH₃)CH₃)C₆ H₁₃), R₁ =(S)-OCH(CH₃) C₆ H₁₃, m=1, n=0, k=1, X₁ and X₂ =NO₂, X₃ and X₄ =H (Scheme VII )was purified by flash chromatography with hexanes/ethyl acetate [95/5 ];R_(f) hexanes/ethyl acetate 85/15]: 0.02. [α]_(D) ²⁵ : +12.0° (c 2.53,CH₃); ¹ H NMR (300 MHz, CDCl₃): δ0.86(t, 6]4, J=6.4 Hz), 1.16-1.54(m,16H), 1.36(d, 3H, J=6.1 Hz), 1.40(d, 3H, J=6.1 Hz), 1.66(m, 2H), 1.80(m,2H), 4.53(m, 1H), 4.64(m, 1H), Distorted AA'BB' System [7.14 (4H)],7.26(d, 1H, J =8.7 Hz), 7.58 (d, 1H, J=8.7 Hz ), 7.68 (dd, 1H, J=2.4 Hz,J=8.7 Hz), 7.92(d, 1H, J=2.4 Hz), 8.30(dd, 1H, J=2.1 Hz J=8.7 Hz),8.61(d,.¹ H, J=2.1 Hz); 3CNMR (300 MHz, CDCl₃): δ13.97, 19.32, 19.48,22.47, 22,49, 25.06, 25.17, 29.02, 29.10, 31.61, 31.65, 35.98, 36.17,76.57, 114.87, 116.14, 120.91, 122.19, 123.79, 127.76, 127.88, 131.93,132.35, 135.43, 136.62, 140.45, 141.12, 150.36, 150.99, 155.54, 163.18;IR (CHCl₃): 3020, 2940, 2850, 1740, 1610, 1525, 1510, 1490, 1350, 1275,1240, 1175, 1090, 925, 875, 820 cm⁻¹ ; Mass. spectrum, m/z (rel.intensity); 620 (M⁺ 1), (7), 397(8), 278(19), 231(22), 230(10),166(100), 120(12), (14), 69(6), 57(24), 55(10), 43(27)

Anal. Calcd. for C₃₅ H₄₄ N₂ O₈ :C 67.72, H 7.15, N 4.51. Found: C 67.65,H 7.26, N 4.48.

(S)-4"-(1-Methylheptyloxy)-3'-nitro-4'-biphenylyl-4-n-decloxybenzoate

The compound of formula III where R₂ =(S)-OCH(CH₃)C₆ H₁₃) and R₁ =C₁₀H₂₁ O (Scheme VIII) was purified by flash chromatography withhexanes/ethyl acetate [99/1]; R_(f) [hexanes/ethyl acetate 95/5]: 0.28[α]²⁵ : 0.88° (c 2.55, CHCl); ¹ H NMR (300 MHz, CDCl₃): δ0.87(t, 6H.J=6.8 Hz), 1.13-1.64(m, 23H), 1.32(d, 3H, J=6.1 Hz), 1.80(m, 3H),4.03(t, 2H, J=6.5 Hz), 4.40(m, 1H), 6.96(d, 4H, J=8.7 Hz), 7.37(d, 1H,J=8.7 Hz), 7.51(d, 2H, J=8.7 Hz), 7.81(dd, 1H, J=2.4 Hz, J=8.7 Hz),8.13(d, 2H, J=8.7 Hz), 8.24(d, H, J=2.4 Hz); ¹³ C NMR (300 MHz, CDCl₃):δ14.03, 14.06, 19.67, 22.55, 22.63, 25.47, 25.93, 29.03, 29.22, 29.27,29.31, 29.51, 31.76, 31.85, 36.41, 68.36, 74.06, 114.48, 116.35, 120.46,122.44, 125.69 , 128.57 , 130.12 , 132.28 , 132.76, 139.81, 142.22 ,142.93, 158.84,164.05, 164.25; IR (CHCl₃): 3020, 2920, 2850, 1740, 1610,1550, 1520, 1480, 1360, 1250, 1170, 1090, 1050, 1010, 825 cm⁻¹ ; Massspectrum, m/z(rel.intensity): 603(M⁺ 0.23), 261(100), 121(70), 71(5),69(5), 57(15), 55(10), 43(27).

Anal. Calcd. for C₃₇ H₄₉ NO₆ : C 73.60, H 8.18, N 2.32. Found: C 73.48,H 8.31, N 2.32.

We claim:
 1. A chiral nonracemic compound of formula: ##STR27## where nand m are 0 or 1, with the proviso that one of n or m is 1; k is 1 and Bis COO or OOC;R₁ is --OR_(a), --COOR_(b) or R', where: R_(a) is astraight-chain or branched alkyl or monoalkene group having from 2 to 16carbon atoms; R_(b) is a straight-chain or branched alkyl or monoalkenegroup having from 2 to 15 carbon atoms; and R' is a straight-chain orbranched alkyl or monoalkene group having 1 to 20 carbon atoms where oneor more of the non-neighboring carbon atoms in R', except anyunsaturated carbon atoms, may be replaced with O, S or a Si(CH₃)₂ group;and R* is a chiral nonracemic tail group selected from the groupconsisting of --O--C*H(CH₃)R_(c), --O--C*H(CH₃)COOR_(a) and --O--CH₃C*HF--C*HF--R_(e) in which the * indicates an asymmetric carbon enrichedin one stereoconfiguration which for --O--CH₂ C*HF--C*HF--R_(e) iseither the (S,S) or (R,R) stereoconfiguration where: Rhd c is astraight-chain or branched alkyl or monoalkene group having 2 to 15carbon atoms; Ru is a straight-chain or branched alkyl or monoalkenegroup having 2 to 13 carbon atoms and R_(e) is a straight-chain orbranched alkyl or monoalkene group having 2 to 11 carbon atoms whereinin R_(d) or R_(e) one or more non-neighboring carbon atoms, except anyunsaturated carbon atoms, may be substituted with an O, S, or Si(CH₃)₂group.
 2. The compound of claim 1 wherein R₁ is --OR_(a) or--COO--R_(b).
 3. The compound of claim 1 wherein R* is--O--C*H(CH₃)R_(c).
 4. The compound of claim 3 wherein R₁ is --OR_(a).5. The compound of claim 1 wherein R₁ is --OR_(a).
 6. The compound ofclaim 1 wherein R₁ is --OC₁₀ H₂₁.
 7. The compound of claim 1 wherein Bis COO.
 8. The compound of claim 1 wherein n is 0 and m is
 1. 9. Thecompound of claim 8 wherein B is COO, R₁ is --OR_(a) and R* is--OC*H(CH₃) R_(c).
 10. The compound of claim 9 wherein R_(a) is --OC₁₀H₂₁ and R₁ is --OC*H (CH₃) C₆ H₁₃.
 11. The compound of claim 1 whereinR₁ is a straight-chain or branched alkyl group.
 12. The compound ofclaim 1 wherein R₁ is a monoalkene.
 13. The compound of claim 1 whereinn is 1 and m is
 0. 14. The compound of claim 1 wherein B is OOC.
 15. Thecompound of claim 1 wherein R* is --C*H(CHB)COOR_(a).
 16. The compoundof claim 1 wherein R* is --O--CH₂ C*HF--C*HF--R_(e).
 17. The FLC mixturecomprising a compound of claim 1 wherein said mixture also possessessecond order nonlinear hyperpolarizability.
 18. The FLC mixture of claim17 wherein in said compound R₁ is --OC*H(CH₃)R_(c).
 19. The FLC mixtureof claim 18 wherein in said compound R₁ is OR_(a) where R_(a) is astraight-chain or branched alkyl or monoalkene group.
 20. The FLCmixture of claim 19 wherein in said compound n=0, m=1 and B is COO. 21.A chiral smectic A liquid crystal material which comprises a compound offormula: ##STR28## where n and m are 0 or 1, with the proviso that oneof n or m is 1; k is 1 and B is COO or OCC;R₁ is --OR_(a), --COOR_(b) orR' where: R_(a) is a straight-chain or branched alkyl or monoalkenegroup having from 2 to 16 carbon atoms; R_(b) is a straight-chain orbranched alkyl or monoalkene group having from 2 to 15 carbon atoms; andR' is a straight-chain or branched alkyl or monoalkene group having from1 to 20 carbon atoms where one or more of the non-neighboring carbonatoms in R', except any unsaturated carbon atoms, may be replaced withO, S or a Si(CH₃)₂ group; and R* is a chiral nonracemic tail groupselected from the group consisting of --O--C*H(CH₃)R_(c),--O--C*H(CH₃)COOR_(d) and --O--CH₂ C*HF--C*HF--R_(e) in which the *indicates an asymmetric carbon enriched in one stereoconfiguration whichfor --O--CH₂ C*HF--C*HF-R_(e) is either the (S,S) or (R,R)stereoconfiguration where: R_(c) is a straight-chain or branched alkylor monoalkene group having 2 to 15 carbon atoms; R_(a) is astraight-chain or branched alkyl or monoalkene group having 2 to 13carbon atoms and R_(c) is a straight-chain or branched alkyl ormonoalkene group having 2 to 11 carbon atoms wherein in R_(e), R_(d) orR_(e) one or more non-neighboring carbon atoms, except any unsaturatedcarbon atoms, may be substituted with an O, S, or Si(CH₃)₃ group; andwherein the material exhibits an electroclinic effect.--
 22. Thecompound of claim 21 wherein R₁ is --OR_(a) or --COO--R_(b).
 23. Thesmectic A material of claim 21 wherein R* is --O--C*H(CH₃)R_(c).
 24. Thesmectic A material of claim 23 wherein R₁ is --OR_(a).
 25. The smectic Amaterial of claim 21 wherein R₁ is --OR_(a).
 26. The smectic A materialof claim 21 where B is COO.
 27. The smectic A material of claim 21wherein n is 0 and m is
 1. 28. The smectic A material of claim 27wherein B is COO, R₁ is --OR_(a) and R* is --OC*H(CH₃)R_(c).
 29. Thesmectic A material of claim 28 wherein R_(a) is --OC₁₀ H₂₁ and R* is--OC*H (CH₃) C₆ H₁₃.
 30. The smectic A material of claim 21 wherein R₁is a straight-chain or branched alkyl group.
 31. The smectic A materialof claim 21 wherein R₁ is a monoalkene.
 32. The smectic A material ofclaim 21 wherein n is 1 and m is
 0. 33. The smectic A material of claim21 wherein B is OOC.
 34. The smectic A material of claim 21 wherein R₁is --C*H(CH₃)COOR_(d).
 35. The smectic A material of claim 21 wherein Bis COO, n is 0 and m is
 1. 36. The smectic A material of claim 21wherein the electro-clinic effect is temperature insensitive.
 37. Thesmectic A material of claim 21 wherein the electro-clinic effect has anelectroclinic coefficient greater than 1° of tilt/V/μm.
 38. A non-linearoptical device wherein the non-linear optical material comprises acompound of claim
 1. 39. A non-linear optical device wherein thenon-linear optical material comprises a compound of claim
 2. 40. Anon-linear optical device wherein the non-linear optical materialcomprises a compound of claim
 3. 41. A non-linear optical device whereinthe non-linear optical material comprises a compound of claim
 10. 42. Anon-linear optical device wherein the non-linear optical materialcomprises a compound of claim 1 wherein n is 0, m is 1, B is COO and R₁is --OC*H(CH₃)R_(c).